Immunohistochemical demonstration of serine dehydratase in rat liver.

Serine dehydratase (L-serine hydro-lyase, EC 4.2.1.13) WAS DEMONSTRATED IN LIVER TISSUE OF RATS BY AN INdirect immunofluorescent method. In the adult rat liver, serine dehydratase was localized to periportal hepatocytes, diffusely in their cytoplasm. The enzyme-specific fluorescence was absent or extremely low in the centrolobular hepatocytes. It was not demonstrated in nonparenchymal cells. Feeding a 90% protein diet for 5 days caused marked induction of this enzyme in the periportal and midzonal hepatocytes but no induction in the centrolobular hepatocytes. In the newborn rat liver, there was no apparent intralobular heterogeneity seen in the distribution of serine dehydratase, either before or after dietary induction. After 1 week of age, there was a gradual development of the intralobular hetero-geneity of the enzyme, which was emphasized by dietary stimulation. A comparative study of the induction pattern between the livers of intact and adrenalectomized rats suggested that there is no heterogeneity among serine-dehydratase-positive cells with respect to hormonal regulation of this enzyme by either glucagon or cortisone.