Hemodynamic Effects of the Intraventricular Administration of Angiotensin II and Renin in Awake Dogs

This study was undertaken to investigate the hemodynamic changes induced by intraventricular injections of angiotensin II (A-II), 1 to 100 ng/kg/min, and renin in doses of 0.025 to 0.3 units (u) in conscious instrumented dogs. Angiotensin II produced a dose-related increase in mean arterial pressure; however, only the highest dose produced a significant increase of 23 +/- 6 mmHg. In contrast, renin did not significantly alter mean arterial pressure in the doses administered but 0.1 and 0.3 u induced a significant increase in systolic arterial blood pressure of 10 +/- 2 and 17 +/- 4 mmHg, respectively. Neither A-II nor renin affected heart rate, dP/dt or carotid, coronary or renal blood flows. These data suggest that in conscious dogs, the threshold level of A-II necessary to induce substantial hemodynamic changes is greater than the amount of A-II that can be acutely generated by activation of angiotensinogen. In addition, the present data suggest that the magnitude of the response is dependent on the availability of the substrate rather than the dose of renin injected centrally into conscious dogs.