CLONING OF AN OVINE 11-BETA-HYDROXYSTEROID DEHYDROGENASE COMPLEMENTARY DEOXYRIBONUCLEIC-ACID - TISSUE AND TEMPORAL DISTRIBUTION OF ITS MESSENGER-RIBONUCLEIC-ACID DURING FETAL AND NEONATAL DEVELOPMENT

Glucocorticoids promote the development of many organ systems vital for extrauterine survival, and fetal cortisol provides the trigger for birth in sheep. The activity of glucocorticoids may be influenced at a cellular level by 11beta-hydroxysteroid dehydrogenase (11beta-HSD), which is responsible for the interconversion of cortisol and cortisone. To examine 11beta-HSD gene expression during fetal development, two over-lapping clones which yield a 1.4 kilobase (kb) complementary DNA encoding sheep 11beta-HSD from a liver library were isolated by using a rat 11beta-HSD cDNA as the probe. This cDNA contains a 879 base pair open reading frame for a protein of 292 amino acids that has more than 70% sequence identity to rat and human 11beta-HSDs. To define the tissue distribution of 11beta-HSD messenger RNA in sheep, selected tissues were collected from one fetus at day 130 and term (approximately 145 days), and from a nonpregnant ewe. Cellular RNA was extracted and subjected to Northern blot analysis, and a single 1.8 kb transcript was detected in the fetal and adult liver, lung, hypothalamus, anterior pituitary, and placenta. This was undetectable in adrenals and kidneys, but a smaller (1.5 kb) transcript was present in fetal and adult kidney RNA. The relative abundance of 11beta-HSD mRNA was greatest in fetal and adult livers, and it was much higher in adult liver, lung, and kidney than in the corresponding fetal tissues. To examine whether 11beta-HSD gene expression is developmentally regulated in the fetal sheep, liver, lung, and kidney tissues were taken from fetuses at day 60-70, day 100-110, day 125-130, at term, and from newborn lambs (24-48 h old). In the lung and kidney, the relative abundance of 11beta-HSD mRNA did not change from day 60 to term but increased in the lungs of newborn lambs. In contrast, 11beta-HSD mRNA levels in the liver increased between day 125 and term and rose further in the newborn. Collectively, these results demonstrate that 110-HSD gene expression in sheep is regulated in a tissue-specific and developmentally programmed manner.