Localization of type 8 17beta-hydroxysteroid dehydrogenase mRNA in mouse tissues as studied by in situ hybridization.

The enzyme type 8 17beta-hydroxysteroid dehydrogenase (17beta-HSD) selectively catalyzes the conversion of estradiol (E2) to estrone (E1). To obtain detailed information on the sites of action of type 8 17beta-HSD, we have studied the cellular localization of type 8 17beta-HSD mRNA in mouse tissues using in situ hybridization. In the ovary, hybridization signal was detected in granulosa cells of growing follicles and luteal cells. In the uterus, type 8 17beta-HSD mRNA was found in the epithelial (luminal and glandular) and stromal cells. In the female mammary gland, the enzyme mRNA was seen in ductal epithelial cells and stromal cells. In the testis, hybridization signal was observed in the seminiferous tubule. In the prostate, type 8 17beta-HSD was detected in the epithelial cells of the acini and stromal cells. In the clitoral and preputial glands, labeling was detected in the epithelial cells of acini and small ducts. The three lobes of the pituitary gland were labeled. In the adrenal gland, hybridization signal was observed in the three zones of the cortex, the medulla being unlabeled. In the kidney, the enzyme mRNA was found to be expressed in the epithelial cells of proximal convoluted tubules. In the liver, all the hepatocytes exhibited a positive signal. In the lung, type 8 17beta-HSD mRNA was detected in bronchial epithelial cells and walls of pulmonary arteries. The present data suggest that type 8 17beta-HSD can exert its action to downregulate E2 levels in a large variety of tissues.