Renin-containing Cells Research Articles

Immunohistochemical localization of renin-containing cells in two elasmobranch species.

Renin immunoreactivity was localized at the light and electron microscopic level in two elasmobranch fish species, the Atlantic stingray, Dasyatis sabina, and river ray, Potamotrygon humerosa. At the light microscopic level, the peroxidase-anti-peroxidase method showed a positive immunoreactivity in modified smooth muscle cells in kidney afferent arterioles as well as in arterioles of several organs: rectal gland, inter-renal gland, conus arteriosus, and gill. Electron microscopic renin-positive immunogold localization was confined to the contents of membrane bound granules in the modified smooth muscle cells of these arterioles. The presence of renin-containing granules in the modified smooth muscle, "granular cells," of the renal glomerular afferent arteriole of these two stingray species adds support to earlier studies which showed the structural components of a complete juxtaglomerular apparatus and some of the biochemical and molecular components of a renin-angiotensin system (RAS) as found in teleost fish, reptiles, birds, and mammals. A notable result, however, was the renin-positive immunoreaction in the arteriolar wall of all other organs studied here. The presence of this "diffuse renin system" in the connective tissue of various organs suggests that in these two stingray species in addition to local organ-specific functions, the RAS may act as a systemic mechanism to regulate blood pressure and blood flow in the body.

Recruited renin-containing renal microvascular cells demonstrate the calcium paradox regulatory phenotype

Renin is the critical regulatory enzyme for production of angiotensin (Ang)-II, a potent vasoconstrictor involved in regulating blood pressure and in the pathogenesis of hypertension. Chronic sodium deprivation enhances renin secretion from the kidney, due to recruitment of additional cells from the afferent renal microvasculature to become renin-producing rather than just increasing release from existing juxtaglomerular (JG) cells. JG cells secrete renin inversely proportional to extra- and intracellular calcium, a unique phenomenon characteristic of the JG regulatory phenotype known as the “calcium paradox.” It is not known if renin secreted from recruited renin-containing cells is regulated similarly to native JG cells, and therefore acquires this JG cell phenotype. We hypothesized that non-JG cells in renal microvessels recruited to produce renin in response to chronic dietary sodium restriction would demonstrate the calcium paradox, characteristic of the JG cell phenotype. Histology showed recruitment of upstream arteriolar renin in response to sodium restriction compared to normal-diet rats. Renin fluorescence intensity increased 53% in cortices of sodium-restricted rats (P<0.001). We measured renin release from rat afferent microvessels, isolated using iron oxide nanopowder and incubated in either normal or low-calcium media. Basal renin release from normal sodium-diet rat microvessels in normal calcium media was 298.1±44.6 ng AngI/mL/hour/mg protein, and in low-calcium media increased 39% to 415.9±71.4 ng AngI/mL/hour/mg protein (P<0.025). Renin released from sodium-restricted rat microvessels increased 50% compared to samples from normal-diet rats (P<0.04). Renin release in normal calcium media was 447.0±54.3 ng AngI/mL/hour/mg protein, and in low-calcium media increased 36% to 607.6±96.1 ng AngI/mL/hour/mg protein (P<0.05). Thus, renin-containing cells recruited in the afferent microvasculature not only express and secrete renin but demonstrate the calcium paradox, suggesting renin secretion from recruited renin-containing cells share the JG phenotype for regulating renin secretion.

Adrenergic influences on the development and distribution of renin cells in nephrogenesis

renin-containing cells have generated a great deal of interest, from understanding their characteristic phenotype to following their location during nephrogenesis and evaluating the regulation of their renin-secreting activity by cAMP and β-adrenoceptors. It is now evident that the renin-containing

CBP and p300 in renin homeostasis: can they drive the fate?

CBP and p300 in renin homeostasis: can they drive the fate?

Homeostatic Responses in the Adrenal Cortex to the Absence of Aldosterone in Mice

To study the effects of decreased amounts or absence of aldosterone on development and endocrine function, we have disrupted the mouse gene, Cyp11b2, coding for aldosterone synthase (AS) by replacing its first two exons with sequences coding for enhanced green fluorescent protein. The null pups fail to thrive postnatally, and about 30% die between d 7 and 28. Aldosterone in plasma and AS mRNA in adrenal glands are undetectable in the null mice. Adult AS-null mice are small, weigh 75% of wild type, are hypotensive, have increased concentrations of plasma K(+) and corticosterone, and a decreased concentration of plasma Cl(-). Their plasma renin and angiotensin II concentrations are 45x and 4x wild type. The adrenal cortex is disorganized and has cells that contain marked accumulations of lipid. The zona glomerulosa is widened and includes easily detectable renin-containing cells, not seen in the wild-type adrenal gland. In the AS-/- adrenals, the level of mRNA for Cyp11b1, coding for 11beta-hydroxylase, is 150% wild type. The adrenal glands of the null mice consequently show evidence of a greatly activated renin-angiotensin system and up-regulation of glucocorticoid production. In the AS-null mice enhanced green fluorescent protein fluorescence is mainly at the boundary between the cortex and medulla, where apoptotic cells are numerous. These data are consistent with the absence of aldosterone in the AS-null mice inducing an increased cell-turnover of cells in the adrenals that normally become AS expressing and their migration to the medullary boundary where they apoptose.

Importance of the Renal Nerves for Basal and Stimulated Renin mRNA Levels in Fetal and Adult Ovine Kidneys

To investigate the effect of renal denervation on renin mRNA levels in fetal and nonpregnant adult ovine renocortical tissue and in isolated juxtaglomerular cells under basal conditions and after stimulation. The left kidney was denervated and the right kidney subjected to a sham procedure in nine ovine fetuses (136-141 days' gestation) and 20 nonpregnant ewes. After 5-7 days the denervated and intact kidneys were obtained, and renin-containing renal cortical cells were isolated and cultured overnight. Then cells were treated with isoproterenol, forskolin, or isomethylbutyl xanthine (IBMX) for 4 hours. Total RNA was isolated and renin mRNA measured by RNase protection assay. Cyclic adenosine monophosphate (cAMP) levels were measured in the incubation medium with a competitive enzyme immunoassay. In adults, basal renin mRNA levels were significantly lower in denervated than in sham-operated kidneys. No difference was noted between denervated and intact fetal kidneys. Renin mRNA levels were significantly higher in fetal than in adult kidney tissue, and cells from fetuses had greater increases in renin mRNA after stimulation than did cells from adults. Fetal cells also released more cAMP into the incubation medium, and there was a correlation between cAMP and renin mRNA levels. The data indicate the effects of renal denervation on renin mRNA expression in the kidney are age dependent and that the fetus in late gestation has a mechanism for maintaining renin mRNA levels after denervation, which is absent or nonfunctional in the adult.

RENIN CONTAINING CELLS ARE PRESENT PREDOMINANTLY IN SCARRED AREAS BUT NOT IN DYSPLASTIC REGIONS IN MULTICYSTIC DYSPLASTIC KIDNEY

Hypertension is an important complication of multicystic dysplastic kidney and it has been suggested that it is induced by renin. Little information is available on renin production in this disease. To assess renin production we examined the distribution of renin containing cells in multicystic dysplastic kidneys using immunohistochemical methods. Immunohistochemical examination of renin was performed in 29 multicystic dysplastic kidneys from 14 boys and 15 girls 1 month to 10 years old using rabbit anti-human renin antibodies. In all cases normal renal function was confirmed by the serum creatinine level and no proteinuria on urinalysis. Two patients had the complication of hypertension before removal of the multicystic dysplastic kidney but plasma renin activity was normal. Immunostaining of renin was observed in 26 of 29 multicystic dysplastic kidneys (90%). Histologically multicystic dysplastic kidney involved scarred and dysplastic areas. Renin positive cells were observed predominantly in the scarred areas, mainly in the juxtaglomerular apparatus of mature glomeruli, interlobular arteries and some mature tubules. Immunopositive renin was sparsely noted in the juxtaglomerular apparatus or Bowman's capsules of occasional immature glomeruli in dysplastic areas. Our observations suggest that multicystic dysplastic kidney may have the ability to produce renin. Renin producing cells in the juxtaglomerular apparatus of mature glomeruli and interlobular arteries in the scarred areas may be the predominant source of renin production in this organ.

Increased renin immunostaining in preglomerular arterioles after myocardial infarction in the rat

In previous studies we demonstrated that the intrarenal circulation is vasoconstricted in congestive heart failure (CHF) and that pharmacologic inhibition of the renin-angiotensin system reversed the renal hemodynamic abnormalities. In the current investigation we tested the hypothesis that renin expression is increased in renal arterioles in CHF. Male Sprague-Dawley rats were studied 4 to 6 weeks after left coronary artery ligation and compared with sham-operated and normal age-matched controls. Renal vascular trees were microdissected and immunostained with a polyclonal renin antiserum. Renin immunostaining was localized to the afferent arterioles, with a greater percentage of arterioles staining in rats with CHF (55.3% ± 2.1%) than in sham-operated (43.9% ± 1.9%) or normal age controls (37.6% ± 2.2%). Rats with CHF more frequently exhibited multiple bands of renin staining within a single arteriole (24.9% ± 1.8%) as compared with sham-operated (13.3% ± 1.9%) and normal age controls (11.3% ± 1.4%). Juxtaglomerular apparatus staining was similar in all groups. These data indicate that renin-containing cells are increased in the afferent arteriole in CHF. Increased renin in the preglomerular arterioles may activate local angiotensin production, leading to intrarenal vasoconstriction, reduced nephron blood flow, sodium and water retention, and worsening of congestive heart failure. (J Lab Clin Med 2001;137:21-7)

Intrauterine growth restriction is associated with persistent juxtamedullary expression of renin in the fetal kidney

Intrauterine growth restriction (IUGR) has been linked to impaired renal function and hypertension, suggesting that an adverse prenatal environment could alter kidney development and renin production. Immunohistochemistry and in situ hybridization were employed to localize renin-containing cells (RCCs) in the deep, middle, and superficial zones of autopsy kidney sections, in parallel with histologic maturation, from unexplained stillborn fetuses of normal weight (N = 26) and stillborn fetuses with IUGR (N = 17). In the control group, the number of RCC per 100 glomeruli in the deep zone decreased with advancing gestation from 40 at 20 weeks gestation to five at term (P < 0.001), whereas the opposite change was found in the superficial zone (increase from 5 per 100 to 55 per 100; P < 0.001). In the IUGR group, the density of RCCs in both the superficial and deep zones was similar to the control group at 20 weeks, and no shift in renin gene expression was observed as gestation advanced. Histologic maturation was unaltered. Renin gene expression persists and predominates in the deep renal cortex of the stillborn IUGR fetus, and could contribute to the pathogenesis of neonatal oliguria and/or hypertension during postnatal life.

Beta-adrenergic stimulation of renin expression in vivo

To characterize the effect of beta-adrenergic activation on renal production of renin in the intact organism. Renal expression of renin [renin messenger RNA (mRNA)], plasma renin activity (PRA), inactive renin level, intrarenal renin distribution (immunohistochemistry), and the time course of activation of renin as well as hemodynamic parameters were determined during the subcutaneous infusion of isoproterenol (ISO) into rats. To examine whether beta-adrenergic activation of the renin system is modulated by the rate of salt intake rats were fed diets with normal, low and high salt contents. Systolic blood pressure was not altered. PRA was elevated as much as fourfold after 40 h of ISO infusion. Although renal renin mRNA levels were elevated dose-dependently up to 4.2-fold, no significant recruitment of renin-containing cells could be detected. The time course of PRA revealed a marked transient rise of PRA during 6 h of ISO infusion with a subsequent decline. Inactive renin level was elevated during 3 to 18 h of ISO infusion. In contrast, renin mRNA level increased steadily with a lag phase of 3 h. Infusion of ISO increased PRA and renin mRNA level under a high-salt diet, but had no additional effect either on PRA or on renin mRNA level under low-salt diet. Activation of beta-adrenergic receptors is a powerful stimulus of renin secretion and renin gene expression in juxtaglomerular cells in vivo, albeit the kinetics of upregulation of renin secretion and renin expression are markedly different. Therefore, the sympathetic tone might be a major factor determining the activity of the renin system in vivo. The ability of adrenergic agonists to stimulate the renin system appears to be modulated by the steady-state level of salt intake.

Developmental Changes in Renin-Containing Cells from the Ovine Fetal Kidney

To determine if the increase in intrarenal renin content that occurs in late gestation in the fetal lamb results from an increase in the proportion of cells containing renin, an increase in the amount of renin per renin-containing cell, or both. Kidney cells with a density of 1.062 g/mL were isolated from ovine fetuses at 100-104 days gestation (n = 6, immature) and at 131-139 days gestation (n = 6, mature). This fraction was enriched with renin-containing cells. Total renin (TR) and active renin (AR) were measured by their ability to generate angiotensin I (AI). Renin mRNA was measured by RNase protection assay. The presence of renin in cells and the capacity to release it were identified by immunocytochemistry and cell immunoblot analyses. Data were analyzed by analyses of variance. The TR and AR in isolated cells increased from 3.7 +/- 0.3 and 2.5 +/- 0.2 micrograms AI/microgram protein . hr-1 in immature fetuses to 6.2 +/- 0.7 and 5.0 +/- 0.6 micrograms AI/microgram protein . hr-1 in mature fetuses (P < .01). The percentage of immunopositive renin cells (PC) was greater in mature (40.6 +/- 4.3) than in immature fetuses (15.2 +/- 1.2) (P < .01). The TR/PC and AR/PC were also higher in mature (8.2 +/- 0.6 and 6.6 +/- 0.4 ng AI/h . pc-1) than in immature animals (6.5 +/- 0.6 and 4.4 +/- 0.4 ng AI/h . pc-1) (P < .01). The data indicate that the increase in TR and AR occurring during development in fetal lamb kidney results from an increase in both the number of renin-containing cells and in the renin content per cell.

Developmental Changes in Renin-Containing Cells From the Ovine Fetal Kidney

Developmental Changes in Renin-Containing Cells From the Ovine Fetal Kidney

Developmental changes of isolated renin-containing cells in the ovine fetus.

Developmental changes of isolated renin-containing cells in the ovine fetus.

Identification of ‘renin’-containing cells in the choriodecidua

Chorionic trophoblast, decidual cells, and macrophages have all been named as the site of renin in the placental membranes. To establish more clearly the nature of the renin-containing cells in the placental membranes, double immunostaining techniques were used to stain renin and specific cell markers in the same tissue sections. Cytokeratin was selected as an ectodermal cell marker and CD68 as a cytoplasmic macrophage marker. Cross-binding between antibodies was prevented by blocking species-related binding sites between the first and second sequence of the double-immunostaining procedures and by using highly selective immunostaining techniques in the second sequence. The results clearly show renin immunostaining in CD68-positive macrophages and not in cytokeratin-positive trophoblast. The anti-renal renin monoclonal antibody showed high affinity cross-reactivity with cathepsin D, another aspartic proteinase that can release angiotensin I from angiotensinogen. This should be seen in the context of earlier findings that only two of four anti-renal renin monoclonal antibodies showed staining in uterine and placental tissues and both cross-reacted with cathepsin D. The results indicate that differentiation between renin and cathepsin D and, possibly, other substances with shared properties and epitope homology deserves more attention than it has received thus far.

The effects of ZENECA ZD8731, an angiotensin II antagonist, on renin expression by juxtaglomerular cells in the rat: comparison of protein and mRNA expression as detected by immunohistochemistry and in situ hybridization.

Changes in the mRNA and protein expression of renin-secreting cells in the juxtaglomerular apparatus (JGA) were examined in the rat following administration of ZENECA ZD8731, an angiotensin II receptor antagonist. Doses of 0 or 90 mg/kg were administered daily by gavage for 26 wk. JGA hypertrophy was apparent in histological sections. Immunohistochemistry demonstrated an increase in the number of renin-containing cells in both the afferent arterioles and the interlobular arteries. Similarly, renin mRNA expression, demonstrated by in situ hybridization, had extended to more proximal segments of the afferent arterioles and was also present in efferent arterioles and interlobular arteries. In conclusion, JGA hypertrophy occurred as a result of antagonism of the angiotensin II receptor. Associated with JGA hypertrophy was increased expression of both renin and renin mRNA, indicative of stimulated renin synthesis caused by an exaggerated pharmacological response of renin-secreting cells to the loss of feedback inhibition by angiotensin II.

Expression of renin in coagulating glands is regulated by testosterone.

The presence of extrarenal or local renin-angiotensin system (RAS) has been noted in several tissues, although its functions have not yet been clarified. Renin from the coagulating gland (CG) is the most recently discovered local RAS and is a significant subject for investigation because large amounts of both mRNA and proteins are detected in this organ. Recently, it has been reported that testosterone influences renin synthesis in several extrarenal tissues, although it has no effect on intrarenal renin. Therefore, it is possible that CG renin is also regulated by testosterone. Forty-four male C57BL/6 mice, aged 3 wk to 6 mo, were used in studies on the ontogeny and androgen regulation of the RAS in the CG. The tissues were fixed with Bouin's solution and paraffin sections were stained with immunohistochemical methods using antirenin antiserum. In each immunostained section, the relative number of renin-containing cells in terminal portions of the CG were counted. Immunoreactivity for renin was first detected at 6 wk after birth. After that time, the number of renin-containing cells gradually increased throughout the experiment. In adults, several patterns of renin immunoreactivity were demonstrated in almost all epithelial cells of CGs, specifically; (1) basolateral granular reaction, (2) diffuse immunoreactivity throughout the cytoplasm, and (3) restricted nuclear reaction. Excretory products of some terminal lumina were also found to be positive for renin. At 10 days after castration, renin-containing cells in ductal termini were decreased and remained at low levels until at 4 wk after castration. After testosterone injection, numerical values of renin-containing cells were high at 1 wk and then decreased at 2-3 wk. It is suggested that CG renin of the mouse is expressed together with sexual maturation during development and that it depends on the testis, possibly the male sex hormone.

Immunohistochemical studies of renin-containing cells in the developing sheep kidney.

Renin-containing (RC) cells in small ruminant kidneys have been known to be widely distributed along the blood vessels. In the present study, RC cells in developing sheep kidneys were studied to investigate not only the appearance but distribution with the potential physiological significance using immunohistochemical and histoplanimetrical techniques. Seven fetal, 12 newborn, and 3 adult metanephric kidneys were used and immunostained by anti-renin antiserum. In the histoplanimetrical analysis, the numerical values of RC cells existing at the walls of 3 major arterial types in the kidneys were calculated. At day 44 of gestation, RC cells were already demonstrated in the walls of renal, interlobar, and afferent vessels, located in the deep cortex and the medulla. In intermediate gestational periods, RC cells were detected throughout the intrarenal arterial trees. In late gestational periods, RC cells expressed in the walls of interlobar/arcuate and interlobular arteries tended to decrease or disappear gradually, while they were distributed predominantly in the afferent glomerular vessels. In newborn lambs, especially days 1 to 3 after birth, increased numbers of RC cells were demonstrated throughout the arterial trees in the kidneys. In older lambs, RC cells located in the interlobar/arcuate arteries and the proximal region of the interlobular arteries decreased in number and gradually disappeared. Some RC cells were still distributed in the distal portion of the interlobular artery even in the adult sheep. These results suggest that the wide distribution of RC cells in sheep kidney is formed in perinatal life, and that the neuronal regulation is associated with the maintenance of this distribution.

Angiotensin II type 1 receptor: role in renal growth and gene expression during normal development

To determine whether angiotensin II (ANG II) modulates renal growth and renin and angiotensin type 1 (AT1) gene expression via AT1 during development, weanling rats were given ANG II antagonist losartan (DuP 753) for 3 wk. Body weight (g), kidney weight (g), and kidney weight-to-body weight ratio were lower in losartan-treated rats (162 +/- 7, 1.6 +/- 0.06, and 9.5 +/- 0.1 x 10(-3)) than in control rats (184 +/- 5, 1.8 +/- 0.07, and 10.1 +/- 0.1 x 10(-3); P < 0.05). Renal DNA content (mg/kidney) was lower in losartan-treated (2.4 +/- 0.17) than in control rats (3.3 +/- 0.31; P < 0.05), whereas protein-to-DNA and RNA-to-DNA ratios were similar in losartan-treated and control rats. Renin mRNA levels were sevenfold higher in losartan-treated than in control rats, as determined by quantitative standardized dot blot analysis. In addition, blockade of AT1 with losartan induced recruitment of renin-synthesizing and renin-containing cells in the renal vasculature, as determined by immunocytochemistry and in situ hybridization. To establish whether AT1 blockade has a direct effect on renin gene expression, freshly isolated renin-producing cells were exposed in vitro to losartan (10(-6) M) or culture media (control). Losartan induced a twofold increase in steady-state renin mRNA levels above control (P < 0.05). Intrarenal AT1 mRNA levels were not altered by losartan given either in vivo or in vitro to freshly dispersed cells. To define whether immature renin-secreting cells are responsive to ANG II, renin release was determined by reverse hemolytic plaque assay.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraglomerular expression of alpha-smooth muscle actin in aging mice.

To determine whether chronic treatment with enalapril initiated early in life prevents glomerular injury secondary to normal aging, CF1 mice received enalapril (20 mg/L, n = 10) or nifedipine (40 mg/L, n = 10) in their drinking water from the time of weaning to 12 months of life. Control mice (n = 10) received tap water ad libitum. Immunocytochemical detection of renin confirmed that angiotensin-converting enzyme inhibition resulted in recruitment of renin-containing cells along the preglomerular vessels. Morphometric analysis of glomeruli included assessment of glomerular diameter and the percentage of mesangial area per glomerulus. Glomerular diameter and mesangial area were higher in control mice (99.7 +/- 0.5 microns, 12.7 +/- 0.3%) than in enalapril-treated mice (88 +/- 0.8 microns, 8.6 +/- 0.6%) (P < .05). Glomerular diameter and mesangial area in the nifedipine-treated group (99.1 +/- 0.9 microns, 12.4 +/- 0.9%) were not different from control mice. These results demonstrate that angiotensin-converting enzyme inhibition prevents the glomerular enlargement and mesangial expansion observed during natural aging. In addition, control glomeruli expressed alpha-smooth muscle actin in a mesangial distribution. This effect was prevented by enalapril treatment but not by nifedipine. We conclude that long-term treatment with enalapril from early life prevents the early changes associated with glomerular injury and expression of alpha-smooth muscle actin in the glomerulus. alpha-Smooth muscle actin may participate in and serve as an early marker of the glomerular injury during the normal aging process.

Origin of the Angiotensin II Secreted by Cells

Circulating angiotensin II is unique in that it is formed in the blood by the interaction of circulating proteins. There are in addition many local renin-angiotensin systems in tissues in which angiotensin II is apparently secreted by various types of cells. This brief review considers the possible pathways for synthesis of locally produced angiotensin II in the brain, the anterior pituitary, the testes, the ovaries, the adrenal cortex, the kidneys, the heart, blood vessel walls, and brown and white fat. Synthesis by cells in culture is also reviewed. The possibility that certain cells contain a complete intracellular renin-angiotensin system is not ruled out, but there are problems with this hypothesis. Proteases other than renin may be involved, and there may be different pathways in different tissues. However, it appears that at least in some tissues, angiotensinogen is produced in one population of cells and transported in a paracrine fashion to other renin-containing cells, where it serves as the substrate for production of angiotensin II.