GLUCOCORTICOIDS STIMULATE THE MATURATION OF H,K-ATPASE IN THE INFANT RAT STOMACH

The development of gastric H,K-ATPase from fetal to adult life was stu died in the rat. The alpha and beta H,K-ATPase mRNA abundance, the pro tein abundance, and the enzyme activity increased postnatally, The sha rpest increase in mRNA and enzyme activity was observed in the weaning period, Several intestinal enzymes are known to be stimulated by gluc ocorticoids at the time of weaning. To study the role of glucocorticoi ds in the maturation of gastric H,K-ATPase, we treated 10-d-old rats w ith a single injection of betamethasone. Twenty-four hours after betam ethasone injection, the enzyme activity was significantly higher than in the control animals 12.6-fold, p < 0.05), The abundance of catalyti c alpha H,K-ATPase protein was also increased (2.5-fold, p < 0.01). Th e time-dependent effect of betamethasone on alpha H,K-ATPase mRNA was determined from 6 to 24 h after treatment. Glucocorticoids did not sig nificantly alter the mRNA abundance within 18 h. Twenty-four hours aft er injection, the gastric H,K-ATPase mRNA was significantly increased compared with controls (2.8- and 2.2-fold increase for alpha and beta subunits, respectively, p < 0.01 for both). In conclusion this study i ndicates that glucocorticoids may regulate the long-term maturation of gastric H,K-ATPase by indirectly stimulating enzyme synthesis.