Comparative study of renin-containing cells. Histological approaches

The juxtaglomerular apparatus is known to be the functional unit of renin c ontrol. In the present review, the author will describe the comparative cha racteristics of renin-containing (RC) cells as well as extrarenal distribut ion, paying special attention to developmental and topographical approaches . The characteristic locality of RC cells suggests that the secretion of re nin is performed at a site beside the adventitia or via the glomerular capi llaries. Ontogenetical and phylogenetical investigations of RC cells have p rovided interesting findings on their morphogenesis. Analysis of the endocr ine kidney after unilateral obstruction of the ureter provides some Finding s about the origin of RC cells and the processing of renin granules. Observ ation of developing adrenal renin suggests that there is important involvem ent of angiotensin IT produced by renin synthesis in the morphogenesis of t he adrenal gland in the fetal stage. Coagulating gland (CG) renin is charac terized by testosterone-regulated and exocrine mechanisms. Recently, all or some of the components of the renin-angiotensin system (RAS) have been rep orted 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.