Hypertension, Vol 6, 494-502, Copyright © 1984 by American Heart Association
JE Faber, KW Barron, AC Bonham, R Lappe, EE Muirhead and MJ Brody
Renomedullary tissue has been proposed to exert an antihypertensive
endocrine-like action. The antihypertensive polar renomedullary lipids
(APRL) and neutral renomedullary lipids (ANRL) are potential mediators of
this action. We evaluated the blood pressure and regional hemodynamic
responses to APRL administered peripherally (i.v.) and to the central
nervous system (CNS) in normal rats and rats with sinoaortic
deafferentation (SAD) to remove baroreflex buffering. Rats were chronically
instrumented with Doppler flow probes for measurement of mesenteric, renal,
and hind-quarter vascular resistance, with arterial pressure and
intravenous catheters, and with lateral cerebroventricular cannuli for
intracerebroventricular (i.c.v.) administration. Intravenous APRL (0.01 to
1.0 micrograms) produced a dose-dependent decrease in blood pressure,
tachycardia, and dilation of all vascular beds studied. The dose-response
relationships were shifted to the left in SAD animals. APRL administered
i.c.v. had no effect on intact or SAD rats. Pressor and regional
vasoconstrictor responses to norepinephrine, angiotensin, and vasopressin
were markedly reduced in SAD animals during constant infusion of APRL. In a
second group of conscious SAD animals instrumented for blood pressure and
heart rate measurements, intravenous ANRL (500 micrograms) decreased both
arterial pressure (-45 +/- 16 mm Hg) and heart rate (-50 +/- 16 bpm). When
given i.c.v., however, ANRL (10-100 micrograms) had no significant effect
on resting blood pressure or heart rate. These studies suggest that APRL
and ANRL produce no significant cardiovascular effects that are mediated
through the CNS. However, both lipids are potent depressor agents, and APRL
exhibits a strong peripheral vasodilator action and nonspecifically reduces
reactivity to vasoconstrictor agents.
ARTICLES
Regional hemodynamic effects of antihypertensive renomedullary lipids in conscious rats
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