Cardiovascular and renal effects of isoproterenol infusions in young swine

The cardiovascular and renal effects of intravenous (i.v.) and intra-arterial (i.a.) infusions of isoproterenol (ISP, 0.1-0.2 micrograms/kg/min) were evaluated in 17 two-week-old swine anesthetized with pentobarbital. The glomerular filtration rate (GFR) of each kidney and blood flow and vascular resistance (RVR) of the left kidney were determined in all animals. In the 8 animals given ISP i.v., right ventricular pressure and dP/dtmax were also determined via a thoracotomy. In 9 animals, ISP was given i.a. after stabilization of constant-flow perfusion of the left kidney in situ. During i.v. infusion of ISP, the positive inotropic and chronotropic effects and the decrease in arterial pressure were maintained; renal blood flow and GFR increased and RVR decreased. During i.a. infusion of ISP in the constant-flow perfused kidney, similar changes in RVR and GFR were observed despite the higher effective concentrations of drug reaching the kidney. We conclude that, at this stage of postnatal renal development, the infusion of cardiotonic doses of ISP lowers RVR and produces a small increase in GFR.