CHARACTERIZATION OF CDNAS ENCODING ISOFORMS OF HAMSTER 3-BETA-HYDROXYSTEROID DEHYDROGENASE DELTA(5-]4)ISOMERASE

Western blot analyses of various hamster tissues reveal high levers of expression of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) in adr enal and liver, and moderate levels of expression in kidney. The expre ssion in liver is sexually dimorphic; very high levels of protein are observed in adult male liver but very low levels are seen in the femal e liver. Three distinct cDNAs encoding isoforms of 3 beta-HSD were iso lated from hamster cDNA libraries. The type 1 isoform is a high-affini ty dehydrogenase/isomerase expressed in adrenal and male kidney. The t ype 2 isoform is also a high-affinity dehydrogenase/isomerase expresse d in kidney and male liver. The type 3 enzyme is a 3-ketosteroid reduc tase expressed predominantly in kidney. Sequencing of the clones showe d that all three are structurally very similar, although types 1 and 2 share the greatest degree of similarity. Immunohistochemical staining for 3 beta-HSD in the adrenal was found throughout the adrenal cortex . In the kidney staining was confined to tubules, and in the liver, he avy staining was found in hepatocytes. The cloning of cDNAs for 3 beta -HSD from the liver and kidney should help in elucidating the function of this enzyme in these tissues.