CHRONIC PRESSURE-NATRIURESIS RELATIONSHIP IN DOGS WITH INHERITED ESSENTIAL-HYPERTENSION

A genetic model of essential hypertension in the dog was studied to de scribe the phenotypic expression of the arterial pressure, as well as to determine the relationship between mean arterial blood pressure (MA P), hormone, and renal excretory responses to four different levels of sodium intake (5, 40, 120, 240 mEq/day) delivered intravenously and i sotonically. This model was developed at the University of Pennsylvani a (U/Penn) and termed Pennsylvania hypertensive dogs (PHD). The MAP wa s recorded beat-by-beat, 24 h/day, in 16 dogs. Water and sodium balanc es were determined daily for 4 days at each level of intake and blood samples were collected on the last day of each salt step for analysis of plasma renin activity (PRA), atrial natriuretic peptide (ANP), aldo sterone (ALDO), and vasopressin (AVP). After the study, the dogs were designated as hypertensive (PHD-HT) when the 24-h average MAP was grea ter than 110 mm Hg and systolic pressure was greater than 160 mm Hg. D ogs that failed to meet both criteria were designated as normotensive genetic controls (PHD-NT). Although sodium was retained during the fir st day of each increase of salt intake in both groups, a return to bal ance was observed within the 4 days. There was no apparent change in t he slope of the chronic renal function curve in either group of PHD st udied, although the PHD-HT exhibit a curve shifted to a higher level o f MAP. Plasma hormone levels in both groups of PHD studied responded i n a manner similar to normal mongrel dogs with reductions of PRA, ALDO , elevations of ANP, and no change in AVP. The young PHD-HT studied ar e similar in many ways to a subset of humans with essential hypertensi on, indicating a potential role for PHD in future studies of genetic h ypertension.