Ouabain prevents loss of autoregulation in rat pial arterioles caused by reoxygenation after a brief hypoxic episode

Abstract

Pial arteriolar diameter changes inversely with changes in systemic arterial blood pressure. Such changes are consistent with autoregulatory functions. These responses are reduced by a brief period of hypoxia followed by reoxygenation. By using an open cranial window preparation we assessed the changes in pial arteriolar diameters during blood pressure changes in rats induced by hemorrhage and reinfusion of blood, before and after a brief period of hypoxia. The slopes of the changes in pial arteriolar diameter as a function of mean arterial blood pressure were -0.47 +/- 0.26 micron/mmHg (mean +/- SD; 1 mmHg = 133.3 Pa) before hypoxia and -0.11 +/- 0.23 micron/mmHg after hypoxia in the untreated rats. In ouabain-treated rats, corresponding slopes were -0.42 +/- 0.24 and -0.46 +/- 0.22 micron/mmHg. The observed protective effects of ouabain might be a blockade of the Na-K pump in the sarcolemma of the vascular smooth muscle.

Sodium-potassium-ATPase electrogenicity in cerebral precapillary arterioles

“…Na ϩ pump electrogenicity has a dominant role in cell types, including rod photoreceptors (37), peritoneal mast cells (11), and thalamic neurons (36), and is suspected to be important in visceral and conduit arterial smooth muscle tissues (10). Furthermore, Na ϩ pump functions are of specific interest in the vasculature: endogenous ouabain-like substances are implicated in the generation of hypertension (1), there is potential for the development of Na ϩ pump modulators as novel antihypertensive drugs (14), ouabain prevents loss of autoregulation caused by reoxygenation in pial arterioles (21), and the Na ϩ pump mediates part of the response to endothelium-derived hyperpolarizing factor (9). Also, a truncated isoform of vascular Na ϩ pump has been cloned and appears to be selectively expressed in some arteries (26).…”