Systemic and renal effects of angiotensin II in the freshwater turtle Pseudemys scripta elegans

Abstract

This study examined the renal and systemic effects of angiotensin II (ANG II) in the freshwater turtle, Pseudemys scripta elegans. We infused [Asn1, Val5]ANG II at doses of 1, 10, 100, and 500 ng X kg-1 X min-1 in conscious turtles while monitoring blood pressure, glomerular filtration rate (GFR), urine volume, and plasma and urine electrolytes. Saline (0.6%) was infused for two 1-h control periods at 1 ml X kg-1 X h-1 followed by a 1-h infusion of saline with ANG II added. Saline alone was then infused for either two or three 1-h recovery periods. Control values before ANG II infusion averaged 21 mmHg for blood pressure, 1.8 ml X h-1 for urine volume, and 8.0 ml X kg-1 X h-1 for GFR. At 1 (n = 7) and 10 ng X kg-1 X min-1 (n = 6) ANG II produced no significant changes in blood pressure or renal function. Angiotensin infusion at the higher rates of 100 (n = 6) and 500 ng X kg-1 X min-1 (n = 11) significantly elevated blood pressure during ANG II infusion (29 and 44 mmHg, respectively), while electrolyte excretion remained unchanged. Despite the increased blood pressure, GFR and urine volume tended to decrease. At all infusion rates, plasma electrolytes remained unchanged. The results suggest that ANG II is a potent constrictor of preglomerular vessels in the kidney of the turtle.