THE PRENATAL AND POSTNATAL-DEVELOPMENT OF NA+ K+-ATPASE IN GASTROINTESTINAL ORGANS OF THE RAT - EFFECT OF BETAMETHASONE TREATMENT/

Developmental changes in Na+/K+-ATPase enzyme activity have been docum ented postnatally in a number of organs, but little is known about pre natal levels or the factors affecting them. This study determined the normal developmental patterns of Na+/K+-ATPase activity in the pancrea s, liver, small intestine, kidneys, and colon of pre- and postnatal ra ts. In addition the effect of betamethasone administration on enzyme a ctivity was determined both antenatally and postnatally. The individua l organs showed a variable pattern of maturational change in enzyme ac tivity. In the pancreas, changes in Na+/K+-ATPase activity appeared to reflect the changing ratio of ductular to acinar cells. The pattern o f enzyme activity in the small intestine was similar to that of the ki dney and was inversely related to that of the colon. Enzyme induction by administration of betamethasone was also variable and bore no relat ionship to the DNA/protein ratio. In the preterm rat, betamethasone in creased the Na+/K+-ATPase activity only in the colon. Use of steroids to increase enzyme activity in the colon at an early stage of developm ent may have therapeutic implications for treating abnormalities of po tassium and sodium homeostasis in the preterm infant.