Ultrastructural and stereological studies of hepatocytes in prenatal development of swine.

Ultrastructure of hepatocytes was investigated during pig fetal development from 18 to 113 day post coitum (dpc). Stereological measurements were taken on the electronograms determining the area and perimeter of the cross-sections of cells, the nucleo-cytoplasmic ratio, and the volume density of hyaloplasm, mitochondria, endoplasmic reticulum, lisosomes, dictyosomes, lipids and glycogen. Hepatocytes are not subjected to any greater changes, apart from their shape, until the last three weeks prior to parturition when they accumulate glycogen. The volume density of particular organelles in hepatocytes is variable. Therefore three periods can be distinguished in their development: period of differentiation (18-40 dpc), period of metabolic activity (40-80 dpc) and period of glycogen accumulation (80-113 dpc). These three phases correspond to three periods of hematopoiesis in the embryonic liver which has already been described [1].