Abnormal renal vascular responses to dipyridamole-induced vasodilation in spontaneously hypertensive rats

The objective of this study was to determine whether there were differences in hemodynamic responses of different vascular beds to systemic administra tion of dipyridamole between spontaneously hypertensive (SHR) and normotens ive Wistar-Kyoto (WKY) rats. To this end, systemic hemodynamics and organ b lood flows (using labeled microspheres) were determined in conscious rats b efore and 10 minutes after dipyridamole (4 mg . kg(-1) . min(-1)) infusion. In both the normotensive and hypertensive rats, the dipyridamole infusion reduced arterial pressure by approximate to 20 mm Hg, associated with a dec reased total peripheral resistance and an increased cardiac output. Renal b lood flow decreased significantly in SHR after dipyridamole but remained un changed or increased slightly in the WKY rats. There were no other differen ces in regional hemodynamics, including those of brain, liver, skin, and mu scle, between the WKY and SHR. Antihypertensive treatment completely restor ed normal renal vascular response to dipyridamole. Previous reports had dem onstrated an abnormal coronary hemodynamic response of the SHR. Our data de monstrate that, as with coronary hemodynamics, hypertension selectively ind uced alterations in renal vasculature. These findings may be of importance in identifying the earliest hemodynamic evidence of developing hypertensive nephrosclerosis.