Gene expression of Vit D conversion eyzymes and Ca metaboism in the feto-placental system

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Calcium metabolism is one of the most interesting areas in the endocrinology. Much amount of research have been done to clarify it in the molecular levels. However, the regulating mechanisms in the feto-placental systems are to be clarified. In addition, the mechanism of gene expression of Vit D conversion enzymes in the fetus is a little different from the adult organs. So our research project consisted with (1) studying chronologically the enzymatic characterization of 1-alpha-hydroxylase and 24R-hydroxylase in the mitochondria in the human placenta, (2) analyzing the 1-alpha-hydroxylase and 24R-hydroxylase in the fetal brain, lung, kidney, which has been thought to be exist only in the renal tubules.We have found that the biologically active vitamin D was synthesized in the placenta and is one of the important substances regulating the fetal growth. The activity of 24R-hydroxylase appears around pregnancy 20 weeks and slightly increases until partrition. In the placenta of severe type of IUGR (intrauterine growth retardation), however, only 24R-hydroxylase except 1-alpha-hydroxylase was found. We suspect that the gene expression of this enzyme might be inhibited. The activity of rabbit fetus and neonate, and that of 1-alpha-hydroxylase was also found in the brain, placenta, kidney. In the brain it increased transiently and disappeared after the age of the neonate. These new finding suspects that the vitamin D conversion enzyme system might consist with the two types of the adult and the fetus, appearing transiently. We are trying to characterize these fetal systems, especially of 1-alpha-hydroxylase.