Ontogenesis of cytoplasmic organelles in rat hepatocytes and the effects of prenatal phenobarbital on endoplasmic reticulum development

Abstract

The ontogenesis of liver cytoplasmic organelles was studied by electron microscopy in the rat from the first day of appearance of liver primordium to postnatal day 5. On gestation day 11, numerous ribosomes, a large Golgi complex, prominent centrioles, and a few mitochondria and microbodies were present. The free ribosomes decreased progressively to reach the adult appearance by day of birth. The centrioles, present in almost all cells on days 11 and 13 decreased progressively and were only occasionally seen by day 17 and thereafter. The mitochondria increased progressively in number and complexity. The Golgi complex, large and multiple during fetal life, became single, small, and inconspicuous after birth. The microbodies remained without significant changes throughout development, increased sharply at birth, and remained as such postnatally. Lysosomes, absent throughout prenatal life, appeared in large numbers at birth and acquired the adult pattern at that time. RER became most prominent on gestation day 13. Electron dense material, seen for the first time within the RER cisternae on day 15, increased further until day 20 and disappeared at birth. SER, absent during the early fetal period, appeared for the first time gestation day 20. The number of cells containing SER, as well as the amount of SER, progressively increased. However, SER distribution was still not comparable to that in the adult hepatocyte on postnatal day 5. Our attempts to induce SER formation prior to gestation day 20, its normal time of appearance, using phenobarbital as inducer, were unsuccessful.