Renal, metabolic and hematological effects of trans-retinoic acid during critical developmental windows in the embryonic chicken

All-trans-retinoic acid (tRA), an active metabolite of vitamin A, directly influences the developing kidney, and is a major regulatory signal during vertebrate organogenesis. The aim of the current study was to specifically target potential critical windows in renal development, and assess altered renal function through disruptions in embryonic fluid compartments. In addition, the effect of exogenous tRA administration on embryonic growth and metabolism was determined. Embryos were exposed to 0.1 or 0.3 mg tRA on embryonic day 8. Morphological and physiological measurements were made on days 12, 14, 16 and 18. Embryo wet mass on day 18 was reduced by 23 % (0.1 mg tRA) and 44 % (0.3 mg tRA). tRA exposure elevated mass-specific oxygen consumption in embryos exposed to 0.1 mg (21.2 +/- A 0.3 mu L-1 g(-1) min(-1)) and 0.3 mg (23.4 +/- A 0.4 mu L-1 g(-1) min(-1)) when compared to sham (18.9 +/- A 0.6 mu L-1 g(-1) min(-1)) on day 14, but not subsequent incubation days. Osmolality of blood plasma was transiently lowered in embryos exposed to 0.3 mg tRA between days 14 and 16. Allantoic fluid osmolality was significantly elevated by tRA to 220 mmol L-1 from days 16 to 18 compared to controls. Blood plasma [Na+] was reduced by 17 % over the same period, while allantoic fluid [Na+] was elevated in tRA-treated embryos compared to control embryos. Collectively, our data indicates that exogenous administration of tRA produces significant alterations to the developmental trajectory of the developing embryonic chicken.