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(Hypertension. 1995;25:1172-1177.)
© 1995 American Heart Association, Inc.

Articles

Influence of Intracellular Renin on Heart Cell Communication

Walmor C. De Mello

From the Department of Pharmacology and Anesthesiology, School of Medicine, University of Puerto Rico, San Juan.

Correspondence to Dr Walmor C. De Mello, Department of Pharmacology, School of Medicine, University of Puerto Rico, PO Box 5067, San Juan, PR 00936-5067.

	Abstract

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Abstract The influence of intracellular renin and angiotensinogen on the control of cell-to-cell communication in heart muscle was investigated in cell pairs isolated from adult rat ventricle. Junctional conductance was measured with two separated voltage-clamp circuits. Intracellular dialysis of renin (0.2 pmol/L) caused a decrease in junctional conductance of 29±3.8% (±SEM, P<.05) in 7 minutes. The effect of renin on junctional conductance seems to be mainly due to the synthesis of Ang II because enalaprilat (10^-9 mol/L) dialyzed into the cell caused an appreciable reduction in the effect of renin. The intracellular administration of renin (0.2 pmol/L) plus angiotensinogen (0.4 pmol/L) produced a faster and stronger fall in junctional conductance (84.3±1.35%, P<.05), and the effect was greatly reduced by enalaprilat. The effects of both renin and angiotensinogen on junctional conductance were not related to a fall in surface cell membrane resistance or a change in series resistance. The effect of renin on junctional conductance was blocked by intracellular administration of a renin inhibitor (S 2864). Moreover, renin dialyzed into just one cell of the pair induced rectification of the junctional membrane, which was prevented by enalaprilat. The results support the view that an intracrine renin-angiotensin system in the heart regulates intercellular communication.

Key Words: renin • heart • cell communication

	Introduction

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The concept that renin has intracellular actions emerged from immunochemical observations that renin and angiotensin II (Ang II) coexist in the cells of the juxtaglomerular apparatus.^{1 2} The origin of the intracellular Ang II is not known because Ang I, which is its precursor, was not found inside these cells.² The internalization of the angiotensin receptor complex was then considered a possible explanation for the intracellular presence of Ang II.³ The question of whether the presence of components of the renin-angiotensin system (RAS) is the result of uptake or gene expression is of seminal importance because there are indications that in some systems a correlation exists between plasma and cardiac levels of renin, Ang I, and Ang II.⁴

Recently, recombinant DNA technology is throwing light on the local synthesis of renin. For instance, the use of radiative DNA or RNA sequences complementary to the sequence of the renin gene makes it possible to detect the expression of the renin gene. The demonstration of angiotensinogen mRNA in renal tubuli⁵ and of renin activity in cardiac myocytes⁶ called attention to a possible intracellular RAS. Dostal et al,⁷ using radioactive cDNA probes and in situ hybridization, showed renin and angiotensinogen transcripts in the atrium and ventricle of rats. Moreover, indirect immunofluorescence staining indicated the presence of Ang I, Ang II, and angiotensin-converting enzyme (ACE) inside cultured rat heart cells.⁸

Although this is not definitive evidence that these compounds are synthesized inside the heart cells, the use of in situ hybridization techniques by these authors raises the possibility that the elements needed for the synthesis of the peptides are inside the cells. Moreover, the presence of angiotensinogen mRNAs inside the heart⁹ and the observation that RAS activity is increased in the compensated stage of heart failure when plasma renin-angiotensin activity is normal¹⁰ indicate that the cardiac RAS plays an important role on the regulation of heart function.

The cardiac muscle is composed of myocytes connected by hydrophilic channels (gap junctions) that make possible the flow of molecules and electrical current from cell to cell.^{11 12} Recent observations showed that Ang II added extracellularly reduces the electrical coupling of rat cardiac cells, whereas enalapril increases it.¹³ Furthermore, Ang I dialyzed into the cytosol reduces the junctional conductance, an effect that is blocked by intracellular administration of enalaprilat.¹⁴ This finding indicates that the conversion of Ang I to Ang II inside the cell is responsible for the fall in junctional conductance elicited by intracellular dialysis of Ang I. Indeed, the intracellular administration of Ang II caused a fast decline of junctional conductance, an effect not blocked by enalaprilat but abolished by staurosporine, an inhibitor of protein kinase C.¹⁴

These observations might have important clinical implications because a decrease in junctional conductance leads to slow conduction,¹¹ a factor involved in the generation of reentry and cardiac arrhythmias.¹⁵ In fact, Ang II increases the intracellular resistance and decreases the conduction velocity in isolated rat papillary muscle (De Mello and Crespo, unpublished observations).

Although renin expression has been detected in cardiac muscle,¹⁶ no information is available on whether intracellular renin influences the electrical coupling of cardiac cells. In the present work, this problem was investigated in isolated rat ventricular cell pairs.

	Methods

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Cell pairs were obtained by enzymatic dispersion of adult rat ventricle following the method of Powell and Twist¹⁷ and Tanigushi et al.¹⁸ The heart was removed and immediately perfused with normal Krebs' solution containing (mmol/L) NaCl 136.5, KCl 10.8, MgCl₂ 0.53, NaH₂PO₄ 0.3, NaHCO₃ 11.0, glucose 5.5, and HEPES 5, pH 7.4. After 20 minutes, a calcium-free solution containing 0.4% collagenase (Worthington Biochemical Corp) was recirculated through the heart for 1 hour. The collagenase solution was then washed out with 100 mL recovery solution containing (mmol/L) taurine 10, oxalic acid 10, glutamic acid 70, KCl 25, KH₂PO₄ 10, glucose 11, and EGTA 0.5, pH 7.4. All solutions were oxygenated with 100% O₂.

The ventricles were minced (1- to 2-mm-thick slices), and the resulting solution was agitated gently with a Pasteur pipette. The suspension was filtered through nylon gauze and the filtrate centrifuged 4 minutes at 22g. The cell pellets were then resuspended in normal Krebs' solution. All experiments were done at 36°C.

Suction pipettes were pulled from microhematocrit tubing (Clark Electromedical Instruments) by means of a controlled puller (Narishige), and their tips were polished with a microforge (Narishige). The pipettes, which were prepared immediately before the experiment, were filled with the following solution (mmol/L): KCl 125, NaCl 10, MgCl₂ 3, EGTA 5, and HEPES 10, pH 7.4. The resistance of the filled pipettes (approximately 2 µm in diameter) varied from 0.5 to 1.5 M.

Drugs
Renin (porcine) and angiotensinogen were from Sigma Chemical Co, and enalaprilat was from Merck Sharp & Dohme Laboratories. Polyclonal renin raised against pig renin has cross-reactivity with rat renin,¹⁹ and rat renin cross-reacts with antibodies to pig renin.²⁰ In some experiments, a renin inhibitor (S 2864, kindly provided by Hoescht AG) was used.

Experimental Procedure
All experiments were performed in a small chamber mounted on the stage of an inverted phase-contrast microscope (Diaphot, Nikon). Junctional resistance was determined in cell pairs with the use of two separated voltage-clamp circuits. Gigaohm sealing was achieved in each cell; the surface cell membrane of both cells was then broken by application of a stronger suction (-30 to -65 cm H₂O), and a whole-cell clamp configuration was produced. Each pipette was connected to a separated voltage-clamp amplifier (Dagan Corp), which made it possible to control the nonjunctional membrane potential in each cell as well as the voltage gradient across the intercellular junction.

The experimental procedure consisted of holding the membrane potential of both cells at -40 mV. Cell 1 was then pulsed to 0 mV while the membrane potential of cell 2 was kept unchanged. Voltage was created across the junctional membrane (V₁), and a compensating current of opposite polarity recorded from pipette 2 (I₂) represents the current flowing through the gap junction (Fig 1). The junctional resistance (rj) or conductance can be easily estimated, as I₂ equals -V₁/rj.

View larger version (9K): [in this window] [in a new window]   Figure 1. Diagrams show current flow in a normal ventricular cell pair under voltage-clamp conditions. The holding potential of both cells was -40 mV. Cell 1 was depolarized by a clamp pulse to -20 mV (V1), while the membrane potential of cell 2 remained unchanged. I1 is the sum of current flowing through the surface cell membrane of cell 1 and the current flowing across the gap junction from cell 1 to cell 2; I2 is the junctional current. Pulse duration, 540 milliseconds at right and 100 milliseconds at left.

Series resistances that originated from the tips of the micropipettes were compensated before the experiment and checked periodically during the experiment. When necessary, the junctional conductance was corrected, taking into consideration the changes in series resistance. For this, the following equation²¹ was used:

where Rs₁ and Rs₂ are series resistances for cells 1 and 2, respectively.

The patch electrode solution was changed with the use of fine polyethylene tubing. In this way renin, angiotensinogen, the renin inhibitor, and enalaprilat were introduced into the cell. Voltage and current signals were displayed simultaneously on an oscilloscope (Tektronix 5113) and chart recorder (Gould 2400).

	Results

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Measurements of junctional conductance made on normal cell pairs showed an average value of 100±0.7 nanosimens (±SEM, n=20). When renin (0.2 pmol/L) was dialyzed into the cell, junctional conductance was gradually reduced, reaching a steady level at the end of 7 minutes (Fig 2). Experiments made on 15 cell pairs indicated an average decline in junctional conductance of 29±3.8% at the end of 7 minutes (Fig 3).

View larger version (32K): [in this window] [in a new window]   Figure 2. Tracings show effect of intracellular administration of renin (0.2 pmol/L) on junctional conductance of a single cell pair. A, Before arrow, control; at arrow, renin was introduced into the pipette solution; B, 5 minutes later; C, 7 minutes later. I1, I2, and V1 are as defined in Fig 1 legend. Pulse duration, 100 milliseconds; I2 calibration, 2 nA; V1 calibration, -40 mV.

View larger version (12K): [in this window] [in a new window]   Figure 3. Line graph shows effect of intracellular administration of renin (0.2 pmol/L) on junctional conductance (gj) recorded from 15 cell pairs (A) and suppression of this effect produced by a renin inhibitor (S 2864, 10-9 mol/L) (n=7, B). Vertical lines in A are SEM; junctional conductance values were normalized.

The series resistance compensated at the beginning of the experiment remained unchanged, with the exception of three experiments in which variations in Rs₁ and Rs₂ occurred. Then the values of junctional conductance were corrected with the use of the equation shown in "Methods."

A possible interference of changes in surface cell membrane resistance on the interpretation of these results was investigated by measuring the time constant (t_m) of the cell membrane using the electrotonic potentials recorded from single cells under a current-clamp configuration (Fig 4; see Reference 14¹⁴ ). As t_m=R_mC_m (where R_m is the membrane resistance and C_m the membrane capacitance, which is constant), variations in R_m are reflected in changes of t_m. As shown in the Table, the dialysis of renin (0.2 pmol/L) for 7 minutes did not change significantly the time constant of the cell membrane. In some experiments, a renin inhibitor (S 2864, 10^-9 mol/L) was added to the internal solution together with renin (0.2 pmol/L), and both compounds were dialyzed into the cell for 7 minutes. Fig 3B (average from seven cell pairs) shows that the effect of renin on junctional conductance was completely suppressed by the renin inhibitor.

View larger version (47K): [in this window] [in a new window]   Figure 4. Electrotonic potential recorded from normal single heart cell under current-clamp configuration. Vertical calibration, 10 mV; horizontal calibration, 100 milliseconds.

View this table: [in this window] [in a new window]   Table 1. Lack of Action of Intracellular Renin Administration on the Time Constant of Surface Cell Membrane of Heart Cell

The question of whether renin is altering junctional conductance through the formation of Ang I and its conversion to Ang II or is acting directly on gap junctional resistance was investigated by dialyzing enalaprilat (10^-9 mol/L), an ACE inhibitor, into the cell for 2 minutes after the addition of renin (0.2 pmol/L) to the patch electrode solution. Fig 5 shows the result obtained from a single cell pair and indicates that ACE inhibition causes an appreciable decrease in the effect of renin on junctional conductance, and at the end of 7 minutes an increase in junctional conductance caused by the ACE inhibitor predominates. Experiments performed on 11 cell pairs confirmed these findings (Fig 6).

View larger version (14K): [in this window] [in a new window]   Figure 5. Tracings show influence of enalaprilat (10-9 mol/L) on the effect of renin (0.2 pmol/L) on junctional conductance. A, Before arrow, control; first arrow, renin was added to the internal solution; second arrow, 2 minutes later enalaprilat was added to the pipette solution. B, 7 minutes later, no decline of junctional conductance usually caused by renin; instead, an increase elicited by enalaprilat was seen. I2 and V1 are as defined in Fig 1 legend. Pulse duration, 100 milliseconds; I2 calibration, 2.5 nA; V1 calibration, 20 mV.

View larger version (31K): [in this window] [in a new window]   Figure 6. Bar graph shows appreciable decrease in the effect of renin (0.2 pmol/L) on junctional conductance (gj) elicited by dialysis of enalaprilat (10-9 mol/L) into the cell. Each bar is the average of 11 experiments. Bar labeled A indicates effect of renin alone and B, effect of enalaprilat on renin action. Vertical line at each bar is SEM. In most of these experiments the increase in junctional conductance produced by enalaprilat was only detected after 7 minutes.

The influence of an intracellular RAS on the regulation of junctional conductance was further investigated by dialyzing angiotensinogen (0.4 pmol/L) plus renin (0.2 pmol/L) into the cell and following their influence on junctional conductance. As shown in Figs 7 and 8, the fall in junctional conductance elicited by intracellular administration of angiotensinogen plus renin was greater and faster than that found with renin alone. Within 3.5 minutes after the introduction of angiotensinogen with renin into the pipette, the fall in junctional conductance was 83% (Fig 7), compared with 29% after 7 minutes with renin alone. Experiments performed on 12 cell pairs indicated an average decline of junctional conductance of 84.3±1.35% (P<.05) at the end of 4 minutes (see Fig 8). The stronger and faster effect of the intracellular dialysis of both compounds was not related to variation in the size of the tip of the micropipettes because the characteristics of the pipettes were the same as those used in the dialysis of renin alone. Furthermore, measurements of the time constant (t_m) of surface cell membrane made before and after 7 minutes of the dialysis of angiotensinogen plus renin into the cell showed no significant variation of t_m. Indeed, in four experiments the variation of t_m was 1.93±0.075%, which was not significant (P>.05), ruling out the possible influence of a change in the resistance of surface cell membrane in the interpretation of the results.

View larger version (8K): [in this window] [in a new window]   Figure 7. Tracings show effect of intracellular dialysis of angiotensinogen (0.4 pmol/L) plus renin (0.2 pmol/L) on junctional conductance recorded from a single cell pair. A, Control; at arrow both compounds were introduced into the cell; B, 3.5 minutes later. I2 and V1 are as defined in Fig 1 legend. Pulse duration, 1 second; I2 calibration, 2 nA; V1 calibration, 20 mV.

View larger version (14K): [in this window] [in a new window]   Figure 8. Line graph shows effect of intracellular dialysis of renin (0.2 pmol/L) plus angiotensinogen (0.4 pmol/L) on junctional conductance (gj) (A) and appreciable decrease of this effect elicited by enalaprilat (10-9 mol/L) (B). Vertical line at each point is SEM. In A, each point is the average from 12 cell pairs.

Enalaprilat (10^-9 mol/L) previously dialyzed into the cell for 4 minutes drastically reduced the effect of the intracellular administration of renin plus angiotensinogen on junctional conductance (Fig 8B).

In other experiments in which renin (0.2 pmol/L) was dialyzed into just one cell of the pair, current-voltage relationship analysis showed rectification of the junctional membrane (Fig 9b). Of particular interest was the finding that enalaprilat (10^-9 mol/L) dialyzed into the cell abolished the rectification induced by renin (Fig 9c).

View larger version (13K): [in this window] [in a new window]   Figure 9. Line graph shows current-voltage relationship recorded from a single cell pair in which renin (0.2 pmol/L) was dialyzed for 7 minutes into just one cell of the pair. a, Control; b, 7 minutes after renin; c, abolishment of rectification induced by enalaprilat (10-9 mol/L) added internally.

	Discussion

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The present results indicate that renin administered into the heart cell reduces junctional conductance by 29±3.8% (n=15) within 7 minutes. The decline in junctional conductance seems to depend on Ang II formation because enalaprilat blocked the effect of renin on junctional conductance. Moreover, the intracellular administration of a potent renin inhibitor (S 2864, 10^-9 mol/L) abolished the effect of renin. The lack of action of renin on surface cell membrane resistance indicates that its effect on cell communication was solely related to a decrease in junctional conductance.

In the present experimental conditions the possible role of a rise in intracellular free calcium, or a decline in the intracellular pH on the effect of renin, seems unlikely because of the concentrations of EGTA (5 mmol/L) and HEPES (10 mmol/L) used in the internal solution. However, in vivo, the role of a possible change in intracellular free calcium on the decline of junctional conductance cannot be ruled out.²² Indeed, evidence is available that Ang II increases the calcium current in rat heart cell.²³

The decrease in junctional conductance (29%) elicited by intracellular administration of renin is much smaller than that seen with intracellular dialysis of Ang I or Ang II (see De Mello, 1994). These observations might be related to a small endogenous content of angiotensinogen. When both angiotensinogen and renin were dialyzed into the cell, the decline in junctional conductance was quite fast and quantitatively similar to that described with intracellular administration of Ang I (76%).¹⁴

It seems reasonable to conclude that when the genes of renin and angiotensinogen are concomitantly expressed in heart cells, the possibility of an appreciable fall in gap junctional conductance can be achieved, particularly when the ACE activity is enhanced as in some experimental models of heart failure²⁴ or in the hypertrophied ventricle.²⁵

The rectification of the junctional membrane caused by intracellular administration of renin into just one of the cells of the pair seems to indicate that differences in the renin concentrations among heart cells influence the direction of current flow along cardiac muscle. Normally, there is no rectification of junctional membrane in adult rat heart cell pairs.^{26 27} This loss of the ohmic properties of junctional membrane together with the decline in junctional conductance produced by renin are contributing factors to the alteration in the pathways of current flow and the generation of cardiac arrhythmias. The abolishment of the rectification achieved with enalaprilat is another indication that the effect of renin on junctional membrane is related to Ang II synthesis. Interestingly, intracellular dialysis of Ang II (10^-9 mol/L) into just one cell of cell pairs also elicits rectification of junctional membrane (W.C. De Mello, unpublished observations, 1994).

Previous studies made on isolated heart cell pairs indicated that the effect of the intracellular dialysis of 10^-9 mol/L Ang II on junctional conductance was suppressed by previous administration of 10^-9 mol/L DuP 753 (losartan) into the cell.¹⁴ Since this compound is a nonpeptide type 1 Ang II receptor (AT₁) antagonist,^{28 29} it is reasonable to conclude that the binding of Ang II to a cytosolic receptor similar to AT₁ is an essential step in the series of events that culminate with the decline of junctional conductance. Interestingly, the intracellular administration of DuP 753 did not abolish the effect of Ang II added to the bath.¹⁴

The results presented above support the view that the activation of a possible intracrine RAS in the heart is involved in the local regulation of cell functions, including intercellular communication. An autocrine and paracrine RAS seems also implicated on the control of cell homeostasis.^{30 31} According to these views, the renin synthesized inside the heart cell leads to the synthesis of Ang II which might promote growth through its effect on the nucleus, can diffuse out of the cell and interact with Ang II receptors at the surface cell membrane, or even activate Ang II receptors located at the cell membrane in nearby cells, promoting changes in contractility, junctional conductance, or growth (see Fig 10). Further studies will be needed to clarify the physiopathologic role of an intracrine RAS in the heart.

View larger version (13K): [in this window] [in a new window]   Figure 10. Diagram illustrates possible role of intracellular renin on an intracrine, autocrine, and paracrine renin-angiotensin system in the heart. Ang II indicates angiotensin II.

	Acknowledgments

 
This work was supported by grants from the National Institutes of Health (532943), the Research Center for Minority Institutions Program, and Merck Sharp & Dohme. I want to thank M. González Castillo for technical help.

Received December 9, 1994; first decision January 27, 1995; accepted January 27, 1995.

	References

Top Abstract Introduction Methods Results Discussion References

 
1. Celio MR, Inagami T. Angiotensin II immunoreactivity coexists with renin in the juxtaglomerular granular cell of the kidney. Proc Natl Acad Sci U S A. 1981;78:3897-3900. [Abstract/Free Full Text]

2. Hackenthal E, Mertz RM, Buhrle CP, Taugner R. Intrarenal and intracellular distribution of renin and angiotensin. Kidney Int. 1987;31(suppl 20):4-17.

3. Taugner R, Hackenthal E. On the character of the secretory granules in juxtaglomerular epithelioid cells. Int Rev Cytol. 1988;110:93-131. [Medline] [Order article via Infotrieve]

4. Danser AHJ, Kats JP, Admiraal PJJ, Derkx FHM, Lamero JMJ, Verdow PD, Saxena PR, Schalekamp MADH. Cardiac renin and angiotensin: uptake from plasma versus in situ synthesis. Hypertension. 1994;24:37-48. [Abstract/Free Full Text]

5. Ingelfinger JR, Zuo WM, Fon EA, Ellison KE, Dzau V. In situ hybridization evidence for angiotensinogen messenger RNA in the rat proximal tubule. J Clin Invest. 1990;85:417-423.

6. Dzau VJ, Re RN. Evidence for the existence of renin in the heart. Circulation. 1987;73(suppl I):I-134-I-136.

7. Dostal PE, Rothblum KN, Chermin MI, Cooper GR, Baker KM. Intracardiac detection of angiotensinogen and renin: a localized renin-angiotensin system in neonatal rat heart. Am J Physiol. 1992;263:C838-C850. [Abstract/Free Full Text]

8. Dostal DE, Rothblum KN, Comrad KM, Cooper G, Baker KM. Detection of angiotensin I and II in cultured rat cardiac myocytes and fibroblasts. Am J Physiol. 1992;263:C851-C863. [Abstract/Free Full Text]

9. Lindpaintner K, Jin M, Niedermaier N, Wilhelm MJ, Ganten D. Cardiac angiotensinogen and its local activation in the isolated perfused beating heart. Circ Res. 1990;67:564-573. [Abstract/Free Full Text]

10. Dzau VJ, Pratt RE. Cardiac, vascular and intrarenal renin-angiotensin systems in normal physiology and disease. In: Robertson JIS, Nicholls MG, eds. The Renin-Angiotensin System. New York, NY: Gower Medical Publishing; 1993;1:42.1-42.11.

11. De Mello WC. Cell-to-cell communication in heart and other tissues. Prog Biophys Mol Biol. 1982;39:147-182. [Medline] [Order article via Infotrieve]

12. De Mello WC. Gap junctional communication in excitable tissues: the heart as a paradigma. Prog Biophys Mol Biol. 1994;61:1-35. [Medline] [Order article via Infotrieve]

13. De Mello WC, Altieri P. The role of renin-angiotensin system in the control of cell communication in the heart: effects of enalapril and angiotensin II. J Cardiovasc Pharmacol. 1992;20:643-651. [Medline] [Order article via Infotrieve]

14. De Mello WC. Is an intracellular renin-angiotensin system involved in the control of cell communication in heart? J Cardiovasc Pharmacol. 1994;23:640-646. [Medline] [Order article via Infotrieve]

15. Hoffman BF, Rosen M. Cellular mechanisms of cardiac arrhythmias. Circ Res. 1981;49:69-83.

16. Dzau VJ, Ellison KE, Brody T, Ingelfinger J, Pratt RE. A comparative study of the distribution of renin and angiotensinogen messenger ribonucleic acids in rat and mouse tissues. Endocrinology. 1987;120:2334-2338. [Abstract/Free Full Text]

17. Powell T, Twist T. A rapid technique for the isolation and purification of adult cardiac muscle cells having respiratory control and a tolerance to calcium. Biochem Biophys Res Commun. 1976;72:327-333. [Medline] [Order article via Infotrieve]

18. Tanigushi Y, Kokubun S, Noma A, Irisawa H. Spontaneously active cells isolated from the sinoatrial and atrioventricular node of the rabbit heart. Jpn J Physiol. 1981;31:547-558. [Medline] [Order article via Infotrieve]

19. Hirose S, Workman N, Inagami T. Specific antibody to renal renin and its application to the direct radioimmunoassay of renin in various organs. Circ Res. 1979;45:275-281. [Abstract/Free Full Text]

20. Takii Y, Figueiredo AFS, Inagami T. Application of immunochemical methods to the identification and characterization of rat kidney inactive renin. Hypertension. 1985;7:236-243. [Abstract/Free Full Text]

21. Giaume JC. Application of the patch-clamp technique to the study of junctional conductance. In: Peracchia C, ed. Biophysics of Gap Junction Channel. Boca Raton, Fla: CRC Press; 1991:175-188.

22. De Mello WC. Effect of intracellular injection of calcium and strontium on cell communication in heart. J Physiol (Lond). 1975;250:231-245. [Abstract/Free Full Text]

23. Allen IS, Cohen NM, Dhallan RS, Gaa ST, Lederer WJ, Rogers TB. Angiotensin II increases spontaneous contractile frequency and stimulates calcium current in cultured neonatal rat heart myocytes: into the underlying biochemical mechanisms. Circ Res. 1988;62:524-534. [Abstract/Free Full Text]

24. Hirsch AI, Talsness CE, Schunkert H, Martin P, Dzau VJ. Tissue-specific activation of cardiac angiotensin converting enzyme in experimental heart failure. Circ Res. 1991;69:475-482. [Abstract/Free Full Text]

25. Schunkert H, Dzau VJ, Tang SS, Hirsch AT, Apstein CS, Lorell BH. Increased rat cardiac angiotensin converting enzyme activity and mRNA expression in pressure overload ventricular hypertrophy: effects on coronary resistance, contractility and relaxation. J Clin Invest. 1990;86:1913-1920.

26. Weingart R. Electrical properties of the nexus membrane studied in rat ventricular cell pairs. J Physiol (Lond). 1986;370:267-284. [Abstract/Free Full Text]

27. De Mello WC. Effect of isoproterenol and 3-isobutyl-1-methylxanthine on junctional conductance in heart cell pairs. Biochim Biophys Acta. 1989;1012:291-298. [Medline] [Order article via Infotrieve]

28. Chin AT, Durecia JV, McCall DE, Wong PC, Price WA, Thoolen MJMC, Carim OJ, Johnson AL, Timmermans PBMWM. Non peptide angiotensin II receptor antagonists, III: structure-function studies. J Pharmacol Exp Ther. 1989;250:867-875.[Abstract/Free Full Text]

29. Wong PC, Price WA, Chin AT, Carini DJ, Duncia JV, Johnson AL, Wexler RR, Timmermans PBMWM. Nonpeptide angiotensin II receptor antagonists. Hypertension. 1990;15:823-834.[Abstract/Free Full Text]

30. Dzau VJ, Gibbons GH. Autocrine-paracrine mechanisms of vascular myocytes in hypertension. Am J Cardiol. 1987;60:991-1031.

31. Lee MA, Böhm M, Paul M, Ganten D. Tissue renin-angiotensin systems: their role in cardiovascular disease. Circulation. 1993;87(suppl IV):IV-7-IV-13.

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