Renal Hemodynamics in Canine DOCA-Salt Hypertension: Effect of Calcium Channel Blockade.

Abstract

Systemic arterial blood pressure (BP), renal blood flow (RBF), and renal vascular resistance (RVR) were followed for 3-4 wks during the progression of DOCA-salt hypertension in the conscious dog. Accompanying the gradual increase in BP was an increase in RBF ; however, RVR was unchanged. The hypertension was totally reversed 5-7 days after cessation of DOCA-salt treatment, but the increase in RBF persisted, presumably as a result of renal hypertrophy. Renal adrenoceptor blockade with prazosin (6 dogs) and prazosin plus idazoxan (4 dogs) caused a comparable decrease in BP in the normotensive and DOCA-salt hypertensive dog ; however, RVR was decreased only in the normotensive. Similar results were obtained during ganglionic blockade with hexamethonium. The i.v. infusion of diltiazem for 1 wk restored BP of the hypertensive dog to a normotensive level, and hexamethonium given i.v. had little further effect on either BP or RVR. These results suggest a non-neurogenically mediated mechanism of canine DOCA-salt hypertension that is susceptible to calcium channel blockade, calcium channel blockers ; hypertension ; desoxycorticosterone ; renal blood flow ; renal hemodynamics Desoxycorticosterone acetate-salt hypertension has been studied intensively for many years, using the rat model. The consensus is that the sympathetic nervous system plays an integral role in the etiology of this form of hypertension in the rat (DeChamplain et al. 1969;Takeda and Bunag 1980;Koepke et al. 1986). Increased basal sympathetic vascular tone as well as enhanced sympathetic activity during stress are believed to contribute to the hypertension. More recently, evidence has been presented for involvement of the central reninangiotensin system in the DOCA-salt hypertensive rat (Basso et al. 1985 ;Igarashi et al. 1985;Itaya et al. 1986). Much less is known about the mechanisms mediating steroid hypertension in the dog ; however, it would seem that the sympathetic nervous system does not play a primary role in canine DOCA-or DOCA-salt hypertension (Bravo et al. 1977 ;Zeigler and Zimmerman 1987;Ueno