Comparison of the response of renal sodium excretion to almitrine and hypoxia in conscious normotensive and spontaneously hypertensive rats.

The effect of hypobaric hypoxia and almitrine on renal sodium excretion and systolic blood pressure was investigated in conscious adult normotensive control rats (NCR) and spontaneously hypertensive rats (SHR). Moderate hypoxia caused a significant natriuresis within the first two days in both NCR and SHR. The systolic blood pressure was significantly diminished in SHR only. Oral application of almitrine (1.0 mg/kg b.w.) induced natriuresis in SHR and NCR. However, there are considerable differences in the pattern of natriuresis between the animals of both strains and when compared to the effect of hypoxia. The urinary sodium excretion by almitrine was not associated with a decrease in systolic blood pressure neither in SHR nor in NCR. The results indicate that both hypoxia and almitrine induce a strong natriuresis in conscious rats apparently by different mechanisms. However, there is no real evidence at present as to whether the peripheral arterial chemoreceptors are indeed involved in these mechanisms, or not, and if so, to what degree.