Analysis by immunocytochemistry and in situ hybridization of renin and its mRNA in kidney, testis, adrenal, and pituitary of the rat.

Abstract

Renin gene expression in cells and tissues of the rat was examined by in situ hybridization histochemistry and immunocytochemistry. By using a mouse cDNA probe, hybridization histochemistry revealed renin mRNA in the renal juxtaglomerular cells, testicular Leydig cells, adrenal zona glomerulosa cells, the intermediate lobe of the pituitary, and scattered cells of the anterior lobe of the pituitary. With four separate antisera to mouse submaxillary renin, there was immunoreactivity in the renal juxtaglomerular cells. However, only one of the antisera stained the Leydig cells, a second stained the adrenal zona glomerulosa, a third stained the intermediate lobe of the'pituitary, and a fourth stained scattered cells of the anterior lobe of the pituitary that were identified as gonadotrophs. The variations with the different antisera in detecting extrarenal renin are unexplained but could imply that posttranslational proteolysis or glycosylation of preprorenin varies in different tissues with consequent variations in immunoreactivity. The finding of renin mRNA and renin-like immunoreactivity in these tissues supports the notion that these tissues are sites for production of renin.Renin of renal origin plays an important role in the control of blood pressure by cleaving angiotensinogen into angiotensin I. It is synthesized as a preprorenin that is converted to prorenin and then into active mature renin by proteolytic cleavage (1). In nephrectomized rats, circulating active renin falls to undetectable levels (2), indicating that most or all of the circulating active renin is of renal origin. However, prorenin is still readily detectable and even increases in the plasma of nephrectomized rats (3). These data suggest that some extrarenal tissues also express the renin gene.Studies using renin activity assays of whole tissue extracts have detected renin-like activity in many different extrarenal tissues. These include the submaxillary glands (4), uterus (5, 6), placenta (7), brain (8, 9), anterior pituitary (10), testis (11), and adrenals (12, 13) of rats, rabbits, humans, and other mammalian species. In most ofthese studies, inhibition ofthe renin activity by specific renin antibodies and determination of the pH optimum have separated the renin-like activity from other enzymes that can generate angiotensin. In some instances, immunocytochemistry or enzymatic assays in specific tissue fractions provided information about the localization of renin in the tissue; examples include the rat adrenal glomerulosa (14, 15), the inner cortex of the mouse adrenal (16), the Leydig cells of the rat testes (17, 18), the renal juxtaglomerular cells of rodents (19), and the gonadotrophs of the rat pituitary (20).However, the presence of renin in a tissue does not demonstrate synthesis of the protein in the tissue; a better indication that renin is actually produced is demonstration of its mRNA in the tissue. In mouse kidneys, adrenals, and testes, renin mRNA has been detected by hybridization of total tissue RNA (21). However, th...

Angiotensin converting enzyme inhibition reduces retinal overexpression of vascular endothelial growth factor and hyperpermeability in experimental diabetes

“…The presence of a local as distinct from a systemic renin-angiotensin system (RAS) has been established in several organ systems [52,53] including the eye where the presence of all components of the RAS including its receptors have been identified [8, 54±56]. The beneficial effect of ACE inhibition on retinopathy in patients with diabetes was recently shown in the EUCLID study where treatment with lisinopril was associated with a statistically significant reduction in the progression of retinopathy [11] confirming the results of several earlier trials with ACE inhibitors in which the benefits achieved approached but did not reach pre-defined levels of statistical significance [60±62].…”

Molecular Biology of Human Renin and Its Gene

“…In this way, lines that express relatively larger quantities of prorenin were obtained from the original transfected cells. Prorenin was subsequently isolated from these cells and was either purified as such or converted to renin by trypsin treatment and purified [7,29,35]. The properties of the purified prorenin and renin were identical to those of naturally occurring renin in all of a number of parameters studied, such as mobility on several gels, apparent carbohydrate content, inhibition by pepstatin that blocks renin activity, substrate affinity, and activation by trypsin [16,28,35].…”

“…Most other tissues that have been found to express the renin gene apparently release only prorenin [ 12,14,[20][21][22][23][24][25][26][29][30][31]. These data could imply that the prorenin processing enzyme has a highly restricted tissue distribution; however, the prorenin synthesized by the transfected AtT-20 cells was cleaved to active renin at the natural cleavage site (documented by amino terminal sequencing), and the release of renin was regulated by the same stimulus (cAMP; in this case, 8Br-cAMP) that promotes the release of renal renin [32].…”

“…The tissue-specific expression of the gene in the rat was examined by hybridization histochemistry and immunocytochemistry [29]. The gene is most actively expressed in the renal juxtaglomerular cells, but there are lower levels of expression in the adrenal glomerulosa, testicular leydig cells, ovary, and anterior and intermediate pituitary.…”

Differential extra-renal expression of the mouse renin genes

“…Previous studies have focussed largely upon renin gene expression in the kidney and SMG of the mouse (4,9,18). Recent work has, however, demonstrated the presence of renin mRNA in the heart and brain of rats and mice (19,20). Using RNase-protection analyses, a triplet sequence mis-match in exon two (14,15) (21), and renin mRNA has recently been detected by a nuclease-protection assay in rat liver (22).…”