Does prenatal undernutrition impair volume control in adult via inadequate expression of aquaporin 2?

Abstract

Coturnix coturnix quail (q) kidneys express AQP2 that is enhanced by dehydration, providing a unique model for examining the effects on adults of environmental challenges during development. We investigated whether undernutrition (UN) in the embryonic period leads to impaired volume regulation via impaired development of kidneys and AQP2. We examined: 1) nephron growth and qAQP2 mRNA expression (in situ hybridization of riboprobes) in quail embryos, intact (CT) or with UN (5–10% of egg white withdrawn); and 2) effects of embryonic UN or 48 h post-hatch food deprivation (FD) on qAQP2 responses in adults after 72 h water deprivation. We found that qAQP2 mRNA is first expressed in medullary collecting ducts (CD) of metanephros at embryonic day 10 (E10) and that mRNA distribution and intensity increased with maturation. In UN embryos, qAQP2 mRNA was seen in medullary CD at E10–E15, but expression in the cortical area of neonatal kidneys was lower than in CT. Birth weight, hatching rate, and kidney size were lower than in CT (P < 0.05) or sham (SH) controls. Water deprivation increased plasma osmolality and decreased body weight (%) more in UN (−19.2 ± 0.6, P < 0.01) or FD (−14.9 ± 2.2) than in CT (−10.5 ± 1.0) or SH (−11.8 ± 2.8), but body growth was similar in the 4 groups. qAQP2 mRNA distribution and levels increased after water deprivation, but the increase was less clear in quails with UN or FD. The results suggest that qAQP2 evolved in medullary CD of metanephric kidneys and that inadequate nutrient supply and stress may delay kidney and qAQP2 maturation, possibly leading to impaired volume regulation in adults (supported by NIH HL 52881 and grant from JSPS).