Expression of renin in coagulating glands.

The presence of an extrarenal or local reninangiotensin system has been noted in several tissues, although their functions have not yet been clarified. Renin from the coagulating gland (CG), is the most recently discovered local renin, and is a significant subject for investigation with histological and molecular biological techniques. Dot-like reactions for renin are detected immunohistochemically in the epithelial cells of CGs of the strains C57BL/6 mice. Excretory products of some terminal lumina are also found to be positive for renin. Colloidal gold particles, indicating the presence of renin, are detected in the lysosomal granules, in which they are especially located on the crystalline structure. They are also observed in the production of series of exocrine granules. At the apical region, both reninpositive exocrine and lysosomal granules are secreted by exocytosis. In the development, immunoreactivity for renin is first detected at 6 weeks after birth. After that time, the number of renin-containing cells gradually increase throughout the development. In adults, several patterns of renin immunoreactivity are demonstrated in almost all epithelial cells of CGs. At 4 weeks after castration, renin-containing cells in terminal ducts are decreased and remain at very low levels. After testosterone injection, the numerical value of renin-containing cells is high at 1 week. Finally, renin mRNA is detected in the CGs by Northern blot analysis and hybridohistochemistry. These findings suggest that renin is synthesized depending on testosterone, and released by exocrine secretion.