CARDIORESPIRATORY AND RENAL RESPONSES TO ARTERIAL CHEMORECEPTOR STIMULATION IN EARLY HYPERTENSION

The peripheral arterial chemoreceptors (PAC) modify not only cardiores piratory but also renal hemodynamic and excretory function. There is e vidence that in hypertensive animals and humans the reflectoric action s of the PAC on ventilation and circulation differ from those of normo tensive subjects. However, the influence of these receptors on kidney function of hypertensive subjects is poorly understood. Cardiorespirat ory and renal responses to pharmacological stimulation of PAC by almit rine bismesylate during normoxia were measured in 16 normotensive (NT) and 13 age-matched borderline-hypertensive young men (BHT) undergoing water diuresis. Placebo experiments served as time controls in each s ubject. NT reacted to almitrine with significant rises in heart rate, minute ventilation, and filtration fraction. Renal vascular resistance tended to increase slightly. In BHT the drug caused a significant ris e in heart rate and minute ventilation too, however, this reaction had a longer latency when compared to NT. In contrast to NT, filtration f raction, and renal vascular resistance decreased. Renal fractional sod ium and lithium excretion did not show any clear response to almitrin in NT, but decreased in BHT. The results suggest that the weaker venti latory response in BHT vs NT might indicate a lower reactivity of thei r PAC to almitrine. The different reactions of the renal vascular bed to pharmacological chemoreceptor excitation in mild hypertensives migh t result from a different reactivity of the renal arterioles, whereas the enhanced proximal tubular sodium reabsorption could be due to an e xaggerated increase in efferent renal nerve activity.