effect of food deprivation and refeeding on some renal functions and renal NA+-K+ ATPase activity in rats

Starvation is considered as a safety manner for reduction of weight in obesity taking into consideration the time factor and the ample supply of water. Results of the study proved that the metabolic responses and the changes in renal functions during starvation are reversible. This work was conducted on 28 rats divided into four groups, one control group and three fasted groups for three days with free access to water, two of the fasted groups were refed for two and five days. The body weight, the water intake and urinary output were decreased during starvation then normalized after refeeding. Significant decrease in creatinine clearance, urea excretion, blood bicarbonate and blood pH were observed during starvation, then returned to normal at the end of the fifth day of refeeding. Significant increase in serum sodium was reported while serum potassium was not affected; urinary excretion of sodium and potassium were decreased but all normalized on refeeding. Starvation did not alter serum chloride. Renal Na+ - K+ ATPase activity was significantly increased during starvation and normalized on refeeding

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

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