Detection of coagulating gland renin by hybridohistochemistry

Comparative study of renin-containing cells. Histological approaches

The juxtaglomerular apparatus is known to be the functional unit of renin control. In the present review, the author will describe the comparative characteristics of renin-containing (RC) cells as well as extrarenal distribution, paying special attention to developmental and topographical approaches. The characteristic locality of RC cells suggests that the secretion of renin is performed at a site beside the adventitia or via the glomerular capillaries. Ontogenetical and phylogenetical investigations of RC cells have provided interesting findings on their morphogenesis. Analysis of the endocrine kidney after unilateral obstruction of the ureter provides some findings about the origin of RC cells and the processing of renin granules. Observation of developing adrenal renin suggests that there is important involvement of angiotensin II produced by renin synthesis in the morphogenesis of the adrenal gland in the fetal stage. Coagulating gland (CG) renin is characterized by testosterone-regulated and exocrine mechanisms. Recently, all or some of the components of the renin-angiotensin system (RAS) have been reported to be synthesized and secreted outside of classical organs or tissues. In the future, the real function of local RAS will be clarified by using gene targeting in mice.

A vital role for glycosphingolipid synthesis during development and differentiation

Glycosphingolipids (GSLs) are believed to be integral for the dynamics of many cell membrane events, including cellular interactions, signaling, and trafficking. We have investigated their roles in development and differentiation by eliminating the major synthesis pathway of GSLs through targeted disruption of the Ugcg gene encoding glucosylceramide synthase. In the absence of GSL synthesis, embryogenesis proceeded well into gastrulation with differentiation into primitive germ layers and patterning of the embryo but was abruptly halted by a major apoptotic process. In vivo, embryonic stem cells deficient in GSL synthesis were again able to differentiate into endodermal, mesodermal, and ectodermal derivatives but were strikingly deficient in their ability to form well differentiated tissues. In vitro, however, hematopoietic and neuronal differentiation could be induced. The results demonstrate that the synthesis of GSL structures is essential for embryonic development and for the differentiation of some tissues and support the concept that GSLs are involved in crucial cell interactions mediating these processes.

Expression of renin in the rat liver

Renin is well-known to be a trigger enzyme in the renin-angiotensin system (RAS). In contrast to the classical RAS, the local RAS has recently been noted in several tissues. The local RAS has a function independent from that of the classical RAS, although its physiological principles are not well known. In the present study, we immunohistochemically demonstrated that hepatocytes in the rat express renin. No renin-immunoreactive cells were detected in rat liver at 0 min after death. At 15 min after death, a small number of renin-positive cells was demonstrated in the lamina hepatica, and they increased with time to the end of observation. Immunoreactivity for renin was scarce throughout the cytoplasm, sometimes condensed to below the cell membrane and around the intracellular granules. Histoplanimetrically, the values from 15 min to 120 min after death were significantly different from that at 0 min after death. Hybridohistochemistry revealed no hybrid signals throughout the liver at either 0 min or 30 min, although renin-immunoreactivity was clearly demonstrated in adjacent sections of liver at 30 min after death. In RT-PCR, the radioactivities in kidney and liver at 0 min after death were not different from those at 30 min after death, respectively. These results suggest the existence of hepatic renin in the rat.