Fate of vasoactive biogenic amines and activity of enzyme phenylethanolamine-N-methyltransferase in rat adrenal gland during the course of pregnancy, parturition and postpartum.

Influence of pregnancy, parturition and postparturition upon natural evolution of adrenaline, dopamine and enzyme of adrenaline synthesis, phenylethanolamine-N-methyltransferase in the adrenal gland was studied. Adrenaline content of the adrenal gland showed a progressive decrease from the 14th to the 18th day postcoitum. The mean values for adrenaline remained lower than the value of day 14 throughout the course of pregnancy up to day 21 postcoitum. At parturition (0 to 4 h) adrenaline declined again to its minimum value but was accompanied by an increase in the adrenal adrenaline level 24 h postpartum. The activity of enzyme phenylethanolamine-N-methyltransferase followed a similar pattern of evolution as that of adrenaline during pregnancy and postpartum. Dopamine concentration of the adrenal gland showed nonsignificant increases during days 14--18 postcoitum. At day 20 postcoitum adrenal dopamine was decreased to its minimum value and this decrease persisted up to day 21 postcoitum. At day 22 postcoitum, adrenal dopamine increased sharply to its maximum value but was again back to the level of day 21 at 0 h parturition. At 24 h postpartum, dopamine content decreased maximally again. The results presented here suggest that the content of vasoactive biogenic amines and the enzyme of adrenaline synthesis go through important natural variations during pregnancy, parturition and postpartum from day 14 postcoitum to 24 h postpartum. This phenomenon does not seem to be merely a cyclic effect. All these variations can be attributed to modified endocrine activity of the pregnant animals by correlating natural variations in steroid hormone levels with the observed changes in biogenic amines, since it is well established that most of the hormonal and nonhormonal steroids affect catecholamine regulation. The observed changes in amine levels could have important influence for the termination of pregnancy.