UBC Theses and Dissertations
11 B [i.e. Eleven beta] - Hydroxysteroid NADP Oxidoreductase in mouse foetal tissues Michaud, Nicole Jocelyne
Corticosterone in foetal tissues after injection of the mother with ¹⁴C-corticosterone was determined by acetylation. with ³H-acetic anhydride and crystallization to constant specific activity. The corticosterone content of whole foetal tissue varied between gestational days 13 and 17 from 641 to 300 ng/g respectively. The specific activity of foetal hormone recovered remained essentially constant; after a 15-minute pulse this was as much as one-fourth that of maternal hormone. However, placenta, head and liver showed distinctly different patterns of metabolism, which changed greatly during this time in head and liver, with a decrease in the conversion of corticosterone to 11-dehydrocorticosterone and a rise in foetal liver 113-hydroxysteroid:NADP oxidoreductase activity. This mitochondrial enzyme, Km=33yM, pH optimum 6, which reduces the 11-dehydro metabolite to the biologically active 116-OH compound, increased sharply, raising the relative amount of the latter in foetal tissues from 15 to 91% during this period. One day after removal of maternal adrenals, foetal corticosterone was normal and maternal levels close to normal, indicating ability of foetal adrenals to function. Maternal hormone, however, crossed to the foetus readily and it was considered most likely that, normally, the maternal source predominates. Regardless of origin, foetal or maternal, however, the hormone is maintained in different foetal tissues in a distinct and different manner.
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