The relative roles of corticosterone and thyroxine in the postnatal development of intestinal hydrolases in the rat

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In the rat both corticosterone and thyroxine have been previously implicated as causal factors in the ontogenic changes of jejunal sucrase/ maltase and lactase activities as well as for ileal acid beta-galactosidase activities. Hyperthyroidism in rat pups caused by administration of exogenous thyroxine from day 6 of life resulted in significant increases in serum corticosterone concentrations, as well as sucrase activity when measured on days 14 and 17. It is also known that in rats made hypothyroid from n-propylthiouracil (PTU) treatment a reduction in serum corticosterone results with a concomitant decrease in sucrase and maltase activities, and an increase in lactase activity. When thyroxine or cortisone acetate (CA) was given to hypothyroid pups as replacement treatment both hormones were equally effective in restoring sucrase and maltase to normal by day 21. When the two hormones were combined no further increase in sucrase activity was seen. However, with maltase the combined treatment resulted in a significantly higher activity than with either hormone alone. Either CA or thyroxine was able to decrease lactase activities, though thyroxine had a significantly greater effect than CA. When both treatments were combined, a further significant decrease in activity resulted. [...]

Corticosterone, Thyroxine, Rats--Physiology