PHOSPHOSERINE PHOSPHATASE - DEVELOPMENT FORMATION AND HORMONAL REGULATION IN RAT TISSUES

Phosphoserine phosphatase was measured in rat liver and kidney as a function of age, sex, and treatment with different endocrine or metabolic factors. Several differences were found between liver and kidney in the regulation of this enzyme. The phosphoserine phosphatase activity of adult liver was 595 units per g for males, 383 for females, and for adult kidney of both sexes it was 1266. Estrogen treatment raised the level of phosphoserine phosphatase in kidneys after the age of 25 days but not in livers. The high levels of phosphoserine phosphatase in fetal liver, 2500 units per g, decreased to 900 during the last 4 days of gestation and the first 3 postnatal days. During the same time period kidney phosphoserine phosphatase increased from insignificant levels to about 600 units per g. The administration of hydrocortisone (but not of thyroxine, glucagon, or serine) to fetal rats enhanced the decline of liver phosphoserine phosphatase, suggesting that adrenocortical secretion is the stimulus for the normal decrease in liver phosphoserine phosphatase during late fetal life. The injection of hydrocortisone to the pregnant rat also resulted in lower phosphoserine phosphatase in the livers of her fetuses or newborns. © 1969.