Reflex inhibition of plasma renin activity by increased left ventricular pressure in conscious dogs
Gorman, A.J.; Chen, J.S.
American Journal of Physiology 256(6 Pt 2): R1299-R1307
1989
ISSN/ISBN: 0002-9513 PMID: 2660600 Document Number: 342502
The purpose of the present study was to determine the effects of left ventricular (LV) outflow obstruction on plasma renin activity (PRA) and the contribution from afferent receptors located in the LV myocardium. In chronically instrumented, conscious dogs (n = 12), changes in PRA during a 15- to 20-mmHg decrease in arterial blood pressure were assessed during 1) intravenous infusions of nitroprusside (NP) alone and 2) infusions of NP while peak systolic LV pressure was elevated by acute ascending aortic occlusion (AAO + NP). Infusions of NP alone elicited significant increases in heart rate (24.9 .+-. 5.1 beats/min; P < 0.01) and in PRA [3.31 .+-. 0.53 ng angiotensin I (ANG I) .cntdot. ml-1 .cntdot. h-1; P < 0.01]. These were accompanied by decreases in both LV pressure (-13.8 .+-. 3.6 mmHg; P < 0.05) and left atrial pressure (-3.0 .+-. 0.7 mmHg; P < 0.05). During AAO + NP, LV pressure was elevated to an absolute level of 169.2 .+-. 4.6 mmHg (+53.3 .+-. 4.2 mmHg; P < 0.001), whereas left atrial pressure was not changed. Both the hypotension-induced rise in PRA and tachycardia were significantly inhibited during AAO + NP (+0.59 .+-. 0.29 ng ANG I .cntdot. ml-1 .cntdot. h-1 and +6.3 .+-. 4.6 beats/min, respectively; NS). The topical application of a local anesthetic in the region of the main coronary artery, sufficient to block the heart rate and arterial blood pressure responses to selective LV receptor stimulation by intracoronary veratridine (0.1-0.4 .mu.g/kg), resulted in significant increases in PRA and heart rate during AAO + NP. We conclude from these results that LV receptors with afferent nerves in the region of the main coronary artery and activated by LV pressure contribute to the inhibitory influence of LV outflow obstruction on PRA in the conscious dog. This suggests that LV mechanoreceptors may play an important role in the regulation of renin release.