Changes with gestational age in the nutritional requirements of postimplantation rat embryos in culture.

Rat embryos explanted at 9.0, 9.5, and 10.5 days of gestation were cultured for periods of 61, 49, or 45 h, respectively, in extensively dialysed rat serum supplemented with various combinations of glucose, amino acids, and vitamins. Glucose was found to be a necessary and sufficient energy source for embryos of all three ages, and virtually no development took place in its absence. Only the youngest embryos required free amino acids for good development in dialysed serum, whereas at all three ages, vitamin supplementation was necessary. However, lack of vitamins had a much more marked deleterious effect on the younger embryos than on those explanted at 10.5 d. Experiments with media deficient in individual vitamins showed that for normal development, 9.0-d embryos required a number of vitamins--principally pantothenic acid, riboflavin, inositol, folic acid and niacinamide, whereas 10.5-d embryos needed only riboflavin. For embryos explanted at 9.5 d, the position was intermediate, with riboflavin and inositol the most significant vitamins. Inositol deficiency in embryos explanted at 9.5 d produced a characteristic neural tube defect--failure of closure at the level of the hindbrain. Thus it appears that both the range of micromolecular nutrients and the severity of developmental impairment in their absence decrease with advancing gestational age.