Pressor and Vascular Responsiveness in Renal Prehypertensive Rabbits with a Nonfiltering Kidney

Abstract

This study examined the possibility that the renal tubules are the site of the sensors that respond to renal artery stenosis (RAS) and which initiate the events leading to pressor hyperresponsiveness. A nonfiltering kidney (NFK) was produced in 32 rabbits by 2 hr of total renal ischemia plus permanent ligation of the ureter; the opposite kidney remained undisturbed. Sixteen of these rabbits also received RAS of the NFK. An additional 16 rabbits received RAS without production of a NFK, and 16 more rabbits were sham-operated controls. In acute experiments 3 days later in conscious rabbits, infusions of norepinephrine at several doses resulted in greater increases in mean arterial pressure in the RAS rabbits, with filtering kidneys (2-K, I-clip) and with NFKs (2-K, 1-clip with NFK), than in the NFK rabbits without RAS (2-K control with NFK) or in the control rabbits (2-K control). Measurements of cardiac output revealed greater increases in total peripheral resistance as well as in mean arterial pressure in response to norepinephrine in the RAS rabbits both without and with a NFK. Because production of a NFK in rabbits did not prevent the development of pressor and vascular hyperresponsiveness 3 days after RAS, these studies indicated that the renal sensors that detect changes in the kidney following RAS and which initiate the series of events leading to pressor and vascular hyperresponsiveness, probably are not located in the renal tubules.

Failure of Verapamil and Diltiazem to Attenuate the Pressor Response to Hypothalamic Stimulation: A Possible Mechanism

“…Like many other antihypertensive drugs their hypotensive effects are more pronounced in hypertensive states (Thievant et al 1982). Hypertensive animals or patients also respond more strongly to vasoconstrictor agents (Finch 1971;Folkow et a1 1973;Finch & Haeusler 1974) and the hyperresponsiveness has been shown to occur in both early and late phases of hypertension (Hallback et al 1971;Wells et al 1985). We had earlier reported that pressor response to posterior hypothalamic stimulation is resistant to the inhibitory action of gallopamil or hydralazine while pressor responses to injected noradrenaline or angiotensin were susceptible (Eferakeya 1989;Eferakeya & Osunkwo 1990).…”