Effect of hormones on hydrolase activities and DNA synthesis in kidney of the developing mouse

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Abstract
The postnatal development of brush border enzyme activities, namely maltase, trehalase, alkaline phosphatase, γ-glutamyltranspeptidase, and leucylnaphthylamidase, as well as the ontogenic profile of DNA synthesis has been determined in the mouse kidney. In addition, these parameters were evaluated following daily administration of hormones during 3 days to 8-day-old mice. Insulin or epidermal growth factor induced a 34% increase of maltase activity over that of 11-day-old controls. Trehalase activity was precociously and significantly augmented by cortisone alone or combined with thyroxine (p < 0.05), although thyroxine alone had no influence. Only epidermal growth factor had a significant effect on alkaline phosphatase activity. γ-Glutamyltranspeptidase activity was significantly decreased when insulin and thyroxine were given simultaneously, but was not modified by any of the hormones injected separately. The level of leucylnaphthylamidase activity was enhanced by 70% after cortisone injection, but it was significantly reduced by thyroxine injected in combination with insulin or cortisone. The incorporation of [3H]thymidine into DNA was increased by 107% after epidermal growth factor administration, but it was decreased by 33% after the cortisone treatment. In spite of this precocious reduction, the level of incorporation was still 2 times higher than that in adult mice. These results show that hormones act separately or in cooperation to accelerate or retard the maturation of the suckling mouse kidney.