effect of dehydration and rehydration on renal Na+ - K+ adenosine triphosphatase activity in rats

ABSTRACT

Dehydration-induced natriuresis has been reported in mammals by pervious studies; the mechanism mediating such phenomenon is not clear. The goal of the present work is to evaluate the activity of renal Na+ - K+ adenosine triphosphatase enzyme [Na+ K+ ATPase] as inhibition of this enzyme system is proposed to be the cause of such natriuresis. The work was carried on 3 groups of rats, each of 10; control group, one-day dehydrated group, rehydrated group. Acute water deprivation resulted in an increased plasma sodium concentration and osmolality. A parallel increase in urinary Na+ excretion and osmolality has been observed in addition to chloriuresis and kaliuresis. An unexpected increase in the activity of renal Na+ K+ ATPase was found on the dehydration day. On the rehydration day, plasma and urinary electrolytes were corrected, while the enzyme transport system remained activated. It was concluded that the natriuresis which occurs with water deprivation is a potent physiological response protecting against excessive increases in plasma osmolality. This natriuresis can be explained by a possible humoral natriuretic factor, originating from or regulated by the central nervous system