Isoproterenol-evoked renin release from the in situ perfused kidney. Dose-response characteristics in spontaneously hypertensive and normotensive Wistar rats

We studied the dose-response relationship between renin secretion and isoproterenol administration in the in situ perfused kidney of spontaneously hypertensive (SHR) and normotensive Kyoto Wistar (WKY) rats obtained from two breeding facilities (BioLab and Taconic Farms). Following pulse injections of isoproterenol (doses ranging from 5 x 10^-11 normotension to 5 x 10^-8 M), timed samples of perfusate were collected over a 30-minute period and perfusate renin activity (PeRA) in each sample was determined by radioimmunoassay. Analysis of regression lines constructed from data representing the renin secretory response (quantified by plotting PeRA of each sample against time of collection and measuring the area under the curve) to isoproterenol concentration demonstrated a positive dose-response relationship for WKY (y = 690.87 + 2864.06x, P < 0.05) and SHR (y = 206.56 + 496.54x, P < 0.05) from BioLab and WKY (y = 138.35 + 74.39x, P < 0.05) from Taconic Farms. However, regression analysis of data obtained from studies in Taconic Farms SHR (y = 65.15 + 0.95x, P < 0.05) did not demonstrate a significant relationship between dose and response. Renin secretion was found to be significantly greater in both WKY strains when comparisons were made between the regression coefficients of WKY and SHR obtained from the same breeding facility (BioLab, P < 0.0005; Taconic Farms, P < 0.025). This investigation has established that the release of renin from the kindey elicited by isoproterenol follows a dose-response pattern similar to that observed with other adrenergically mediated responses. Furthermore, the response of the WKY to isoproterenol-evoked renin secretion was consistently greater than that observed in the SHR strains.