Renin Release during Controlled Hypotension with Sodium Nitroprusside, Nitroglycerin and Adenosine: A Comparative Study in the Dog

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Abstract
The hemodynamic effects of i.v. infusions of Na nitroprusside (SNP), nitroglycerin (TNG), and adenosine [cardiovascular drug] were studied in dogs in parallel with quantitative determinations of plasma renin activity (PRA) by radioimmunoassay. The drugs were given for controlled hypotension, and the mean arterial blood pressure (MABP) was decreased to .apprx. 50 mmHg (6.7 kPa [kilo Pascal]). Arterial blood samples for PRA were collected at 10-min intervals. During the last interval the dogs were subjected to hemorrhagic shock. SNP-induced hypotension could be maintained only with a stepwise increase in infusion rate, from 11.8-16.0 .mu.g .times. kg-1 .times. min-1 (P < 0.05). TNG could not produce the desired blood pressure level, but gradually increasing doses induced a gradually decreasing MABP (80-60 mmHg) (10.7-8.0 kPa). During adenosine-induced hypotension, a perfectly stable blood pressure level was maintained without dose adjustments. Both SNP and TNG induced blood pressure-dependent increases in PRA, while no changes in PRA were seen during adenosine-induced hypotension. Nor could hemorrhagic shock, which induced further increases in PRA during SNP- and TNG-induced hypotension, alter PRA during adenosine infusions. Adenosine differs markedly from conventional hypotensive drugs such as SNP and TNG with respect to stability of action and dose requirements; this stability is related to an inhibited increase in renin release.