The age-related characteristics of the hormonal regulation of Na+, K(+)-ATPase activity in the kidney cortex of rats]

The aldosterone binding in isolated distal convoluted and cortical collecting tubules of renal nephrons and the influence of hormonal induction on the Na, K-ATPase activity in membrane fraction of kidney cortex were studied in 10-day- and 2-month-old rats. No reliable difference in aldosterone-specific binding was revealed (0.26 +/- 0.04 and 0.22 +/- 0.03 fmol/mm of tubule length, respectively, at the age of 10 days and 2 months). It was found that Na, K-ATPase activity increased with age from 0.39 +/- 0.06 to 0.72 +/- 0.10 mumol Pi/mg of protein.1 hour.100 microliters. Aldosterone induction caused approximately a 3-fold increase of the enzyme activity in both age groups comparing to the control level. Co-induction of aldosterone and spironolactone resulted in a 50% decrease of Na, K-ATPase activity in adult rats, but did not influence that in young rats. The revealed age-related differences in the mechanism of hormonal Na, K-ATPase regulation are supposed to underlie the absence of physiological reaction of the kidney to aldosterone in early postnatal ontogenesis.