PLACENTAL RESTRICTION ALTERS ADRENAL-MEDULLARY DEVELOPMENT IN THE MIDGESTATION SHEEP FETUS

The aims of this study were to determine whether placental restriction (PR) alters the pattern of localization of the catecholamine-synthesi zing enzymes, dopamine-beta-hydroxylase and phenylethanolamine N-methy ltransferase, and enkephalin (ENK)-containing peptides in the adrenal gland of the midgestation sheep fetus. We also determined the effect o f PR on the content and profile of the molecular mass forms of ENK-con taining peptides in the fetal adrenal medulla. Placental growth was re stricted by removal of most of the placental implantation sites in the uterus before mating. In midgestation, placental and fetal body weigh t were reduced (p < 0.05) in the PR group (n = 8; 237.9 +/- 39.5 g, 56 4.7 +/- 41.6 g, respectively) when compared with the control group (n = 9; 479.1 +/- 36.9 g, 721.2 +/- 22.8 g, respectively). However, combi ned fetal adrenal weight and adrenal cortical and medullary area were similar in the PR and control fetuses. In PR fetuses, distribution of staining for dopamine-beta-hydroxylase, phenylethanolamine N-methyltra nsferase, and ENK-containing peptides in the adrenal medulla was simil ar when compared with the control group; however, staining was less in tense and not all adrenomedullary cells were stained. The total adrena l content of ENK-containing peptides was also significantly (p < 0.05) less in the PR group (103.4 +/- 18.6 ng/adrenal) than in the control group (243.6 +/- 24.8 ng/adrenal). However, the molecular mass profile of ENK-containing peptides was not altered in the PR fetuses compared with controls. These data suggest that placental restriction in utero may alter the synthesis and/or secretion of catecholamines and ENK-co ntaining peptides from the fetal adrenal medulla from as early as 90 d gestation.