CHANGES IN ADRENAL CARBONYL REDUCTASE-ACTIVITY IN PREGNANT RATS

Changes in adrenal carbonyl reductase (CR) activity during pregnancy a nd postparturition in rats were investigated using two substrates, 13, 14-dihydro-15-keto-prostaglandin F-2 alpha (15KD-PGF(2 alpha)) and p-n itroacetophenone (PNAP). 15KD-PGF(2 alpha), reductase activity showed the lowest level on day 16 of pregnancy and steeply increased on the m orning of postpartum day 1. PNAP reductase activity did not change up to day 18 of pregnancy, then was gradually increased and maintained th e highest levels between day 19 and the morning of day 21 of pregnancy . Thereafter, the enzyme activity was rapidly decreased after parturit ion, on the contrary of changes in the 15KD-PGF(2 alpha) reductase act ivity. On the other hand, exogenous glucocorticoid treatment increased the 15KD-PGF(2 alpha), reductase activity and decreased the PNAP redu ctase activity in adrenal glands of nonpregnant animals. Thus, it is f ound that the adrenal CRs in the above two classes are regulated by di fferent mechanisms. As maternal corticosterone level is increased rapi dly during late pregnancy by maternal transfer of fetal corticosterone , the present results suggest that adrenal CR activity during pregnanc y, in particular at periparturition, may be influenced by fetal cortic osteroids.