(Hypertension. 1997;30:345.)
© 1997 American Heart Association, Inc.
Articles |
1-Adrenoreceptor
From the Department of Internal Medicine, Hypertension and Vascular Research Laboratories, University of Texas Medical Branch (Galveston).
Correspondence to Donna H. Wang, MD, Department of Internal Medicine, Hypertension and Vascular Research Laboratories, 8.104 Medical Research Bldg, University of Texas Medical Branch, Galveston, TX 77555-1065. E-mail dwang{at}utmb.edu
Abstract We have previously shown that sodium restriction
upregulates the genes encoding angiotensin II receptor
(AT1) subtypes, AT1A and AT1B, in
the adrenal gland and that this upregulation is mediated by activation
of the AT1 receptor. There are multiple interactions
between the renin-angiotensin and the adrenergic nervous
systems; thus, we conducted the present experiment to investigate
whether low sodium-induced upregulation of adrenal AT1A and
AT1B is modulated by the
1-adrenoreceptor. Seven-week-old male
Wistar rats were divided into four groups and given normal sodium diet
(0.5%, NS), NS+prazosin (3.5 µg · kg-1 ·
min- 1 by osmotic pump), low sodium diet (0.07%, LS), or
LS+prazosin. Body weight and mean arterial pressure were
not modified over the 2 weeks of treatment (P>.05). Pressor
responses to bolus injection of the
1-agonist
phenylephrine were inhibited in both prazosin groups,
compared with NS and LS rats (P<.05). Adrenal
AT1A mRNA, determined by Northern blot analysis,
was increased in LS (P<.05) but not in NS+prazosin
(P>.05), compared with NS. Prazosin enhanced the LS-induced
increase of AT1A mRNA (P<.05). Adrenal
AT1B mRNA was increased in both LS and NS+prasozin rats,
compared with NS rats (P<.05). Prazosin also enhanced the
LS-induced increase in AT1B mRNA (P<.05).
Therefore, blockade of
1-adrenoreceptor
results in an enhancement of LS-induced upregulation of adrenal mRNA
for AT1A and AT1B. These data suggest that the
sympathetic nervous system exerts an inhibitory action, via
activation of the
1-adrenoreceptor, on
AT1A and AT1B gene expression in the adrenal
gland during sodium depletion.
Key Words: receptors, angiotensin receptors, adrenergic, alpha adrenal glands sodium, dietary
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