Fetectomy alters maternal pituitary-adrenal function in pregnant rhesus macaques

The interplay between the fetus and mother may play a key role in the regul ation of primate pregnancy and parturition. This study was designed to test the hypothesis that fetectomy alters maternal pituitary-ad renal function. Between 117 and 122 days of gestation (term = 167 days), six rhesus macaqu es underwent surgery for catheter implantation. At surgery the fetuses were removed while the membranes and placenta were left in situ. Six additional intact catheterized pregnant animals served as controls. Animals were main tained under a 12L:12D cycle with lights-on from 0700 to 1900 h. Beginning at least 1 wk after surgery, maternal arterial blood samples were collected at 3-h intervals for 24 h for hormone and catecholamine analysis. This sam pling protocol was repeated at weekly intervals until cesarean delivery at 151-157 days of gestation. Following fetectomy, plasma ACTH, dehydroepiandr osterone sulfate (DHEAS), and cortisol levels were significantly lower (36% , 35%, and 44%, respectively) compared with control animals (P < 0.05). Des pite a significant reduction in overall levels, the rhythm in maternal plas ma cortisol was maintained following fetectomy. Plasma dopamine and norepin ephrine were also depressed (P < 0.05), whereas epinephrine remained unaffe cted. Our data clearly demonstrate the role of the fetus in the regulation of the maternal pituitary-adrenal axis during gestation. This interaction p lays a significant role in the regulation of maternal endocrine function th at may influence the initiation of labor.