HORMONALLY INDUCED CHANGES IN APOCRINE SECRETION OF TRANSGLUTAMINASE IN THE RAT DORSAL PROSTATE AND COAGULATING GLAND

Coagulating gland and dorsal prostate of the rat are peculiar in secre ting transglutaminase, a protein-cross linking enzyme that is released in an apocrine fashion. To elucidate whether or not the intracellular pathway and the unusual extrusion mechanism proceed constitutively or were differentially regulated, transglutaminase immunoreactivity was studied both at the light and electron microscopic levels. In addition , ultrastructural morphometry and scanning densitometry were applied t o quantitate hormone-dependent distribution of transglutaminase. Coagu lating glands and dorsal prostate, respectively, from sexually active rats were compared to those from sexually inactive, castrated, estradi ol-treated or testosterone-substituted castrated animals. In intact, s exually active animals, no labeling of the cisternae of rough endoplas mic reticulum was seen, but instead the hyaloplasm was labeled. In the supranuclear portions of the cells an increase in labeling density of the hyaloplasm subjacent to the plasma membrane was found, whereas no labeling of either Golgi stacks or vesicles was observed. Apical bleb s projecting into the acinar lumen were densely labeled. In castrated animals, epithelium showed a reduction of rough endoplasmic reticulum, toss of secretory blebs, and a decrease in cell size. Morphometric an alysis of immunolabeling of coagulating gland epithelium from experime ntal animals resulted in a highly significant reduction of labeling of the hyaloplasm and apical blebs which was reversed by testosterone su pplementation of castrated animals. After estrogen treatment, the redu ction in immunolabeling was less pronounced, but morphology of apical blebs was obviously changed. Results from scanning densitometry of Wes tern blots correlated with quantitative immunoelectron microscopical f indings. Northern blot analysis using a secretory transglutaminase cDN A probe showed characteristic changes at the RNA levels. Our results i ndicate that apocrine secretion of transglutaminase in rat coagulating gland and dorsal prostate is a hormonally controlled process, where a ndrogen deprivation results in impaired biosynthesis and release of tr ansglutaminase, whereas estradiol treatment only partially inhibits se cretion, but changes morphological features of the glandular epitheliu m, especially apocrine bleb formation.