Stereological Analysis of Smooth Endoplasmic Reticulum and Peroxisome Proliferation in Hepatocytes from Neonatal and Adult Mice after Phenobarbital Administration

The proliferation of the smooth endoplasmic reticulum and peroxisomes in hepatocytes after phenobarbital administration was stereologically analysed for neonatal and adult ddY male mice. Animals received daily intraperitoneal injections of phenobarbital in a dosage of 35 mg per Kg body weight at 1 and 2 days after birth or for 2 days for the adult. Adult animals were also injected with 150 mg per Kg for 7 days. The animals were killed about 24hours after the last injection. In neonatal animals, phenobarbital administration caused similar amount of smooth endoplasmic reticulum proliferation both in centrilobular and periportal hepatocytes. In adult animals, however, the proliferation occurred only in centrilobular cells after administration of 35 mg per Kg for 2 days, and predominantly in centrilobular cells (not by morphometry) even after administration of 150 mg per Kg for 7 days. Peroxisomes proliferated in centrilobular cells from adult animals injected with 35 mg per Kg for 2 days. The results suggest that there are some differences in the nature of response to phenobarbital between neonatal and fully differentiated adult hepatocytes.