OVINE AQP(1) - CDNA CLONING, ONTOGENY, AND CONTROL OF RENAL GENE-EXPRESSION

The cDNA for the ovine aquaporin 1 (AQP(1)) was obtained and found to be 97%, 88%, and 85%, respectively, homologous to the bovine, human, a nd rat AQP1 cDNA. The level of total kidney mRNA expressed as a ratio to glyceraldehyde-3-phosphate dehydrogenase increased sevenfold from 6 0 days to 140 days of gestation (term=150 days) and reached adult valu es by 6 weeks after birth. Treatment of pregnant ewes (and their fetus es) at 64 and 74 days of gestation with dexamethasone (0.76 mg/h for 4 8 h) resulted in a small but statistically significant increase in AQP (1) mRNA only in the 74-day fetuses. By immunohistochemistry, it was s hown that the increase in AQP1 mRNA with dexamethasone resulted largel y from an increase in maturity of the inner zone of the fetal renal co rtex (i.e., more tubules) as well as stronger expression of AQP(1) in proximal tubules and thin descending limbs of loops of Henle. A simila r effect occurred in fetuses infused for 3 days with angiotensin I (6. 7 mu g/h) in the last third of gestation.