Ovine AQP₁: cDNA cloning, ontogeny, and control of renal gene expression

Abstract.

The cDNA for the ovine aquaporin 1 (AQP₁) was obtained and found to be 97%, 88%, and 85%, respectively, homologous to the bovine, human, and rat AQP₁ cDNA. The level of total kidney mRNA expressed as a ratio to glyceraldehyde-3-phosphate dehydrogenase increased sevenfold from 60 days to 140 days of gestation (term=150 days) and reached adult values by 6 weeks after birth. Treatment of pregnant ewes (and their fetuses) at 64 and 74 days of gestation with dexamethasone (0.76 mg/h for 48 h) resulted in a small but statistically significant increase in AQP₁ mRNA only in the 74-day fetuses. By immunohistochemistry, it was shown that the increase in AQP₁ mRNA with dexamethasone resulted largely from an increase in maturity of the inner zone of the fetal renal cortex (i.e., more tubules) as well as stronger expression of AQP₁ in proximal tubules and thin descending limbs of loops of Henle. A similar effect occurred in fetuses infused for 3 days with angiotensin I (6.7 μg/h) in the last third of gestation.