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Department of Physiology, Medical College of Virginia Richmond, Virginia 23298
Abstract
In an attempt to localize endogenous prolactin (PRL) in rat ventral prostate gland at the light microscope level, the following 4-step immunohistochemical reaction sequence was applied to fixed tissue sections: I) goat anti-monkey
-globulin (AM
G), II) NIAMDD rabbit anti-rat PRL (APRL), III) goat anti-rabbit
-globulin: peroxidase conjugate (AR-
G-per), and IV) chromogenic substrate. AM
G was required to block the nonspecific staining pattern produced by direct binding of AR-
G-per to the tissue and unmask that produced by APRL. APRL-dependent staining occurred in the Golgi region of ventral prostate epithelial cells. Golgi region staining was attenuated and eventually disappeared with increased APRL dilution and was not reproduced when normal rabbit serum or rabbit antisera to rat LH or rat TSH replaced APRL. However, absorption of APRL with highly purified NIAMDD rat PRL (1-1) neither attenuated nor eliminated Golgi region staining. This suggested tliat the APRL-dependent staining of rat ventral prostate gland was not due to endogenous PRL in the tissue. The nonabsorbable APRL-dependent staining pattern is, as yet, unexplained but might involve the binding of the PRL portion of APRLPRL complexes to PRL binding sites in the epithelial cells of ventral prostate gland. To test for PRL binding sites, tissue sections were exposed to varying doses of rat PRL 1-1 before the 4-step immunohistochemical reaction sequence. PRL preincubation produced, in a dose-related fashion, immunospecific Golgi region staining indicative of intracellular PRL binding sites (IPBS). IPBS were androgen-dependent, disappearing after castration and returning when atrophic ventral prostate glands were stimulated by testosterone treatment. In androgen-restored tissue intracellular PRL binding occurred either in the Golgi region or involved the entire cytoplasm. Whether or not androgen-dependent IPBS represent a physiological receptor for PRL in rat ventral prostate gland remains to be determined.
Footnotes
Supported in part by an American Cancer Society Grant (IN 105) to R. J. W.
1 Presented in part at the 1976 Meeting of The Endocrine Society, San Francisco (Prog 58th Ann Mtg Endo Soc: 166, 1976). Address correspondence to: Dr. R. Witorsch, Department of Physiology, Box 608 MCV Station, Medical College of Virginia, Richmond, Virginia 23298.
Received February 1, 1977.
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