Morphological and physiological effects of β‐hydroxybutyrate on rat embryos grown in vitro at different stages

Publisher Website
Google Scholar
Abstract
Diabetic women are more likely to give birth to infants with congenital malformations than are nondiabetic women. Rodent embryos have been used as a model for the study of abnormal fetal development associated with maternal diabetes, and some of the metabolic factors which are altered in diabetes, such as raised glucose and ketones, have been shown to cause abnormal development of rodent embryos in vitro. The present work explores further the teratogenicity of β‐hydroxybutyrate to rat embryos. To determine the sensitivities of rat embryos at different stages of their development, rat embryos at 9.5 days of gestation have been cultured in vitro for 24 or 48 h, with or without 4 × 10−2 M β‐hydroxybutyrate for all or part of the culture period. The ebryos have been examined by scanning electron microscopy, and a detailed morphometric analysis of one tissue, the neuroepithelium, has been undertaken. The results confirm that β‐hydroxybutyrate causes abnormal development of rat embryos. The results of experiments in which embryos were exposed to β‐hydroxybutyrate for only part of a 48 h culture show that embryos expoosed to β‐hydroxybutyrate for a complete 48 h culture are more severely affected than embryos exposed to β‐hydroxybutyrate for only part of the culture and that embryos are more vulnerable to β‐hydroxybutyrate during the first half of a 48 h culture (equivalent to 9.5 to 10.5 days of gestation) than during the second half of a 48 h culture (10.5 to 11.5 days of gestation). The results of experiments in which embryos were cultured with β‐hydroxybutyrate from 9.5 days of gestation for 24 h (equivalent to 9.5 to 10.5 days of gestation) showed that some effects of β‐hydroxybutyrate are already apparent after 24 hours in culture. Many of the abnormalities produced by β‐hydroxybutyrate can be calssified as embryonic retardations rather than malformations—that is, embryos show features characteristic of normal, but younger, embryos. Embryos exposed to β‐hydroxybutyrate for the complete 48 h culture period consume less glucose and produce less lactate than control embryos on a per embryo basis, but not on a per μg protein basis, suggesting that the reduced metabolism is an effect of β‐hydroxybutyrate‐induced developmental delay rathen than a cause of it. Morphometric analyses of the shapes of the cells of the neuroepithelium show that the cells are less elongated/tapered in β‐hydroxybutyrate‐treated embryos than in control embryosd; these differences are characteristic of embryos in which the elevation of the neural fold has been inhibited. The mechanisms by which developmental retardation might lead to fetal malformation are discussed, with special reference to the possible of neural tube defects.
Keywords