Rat Kidney Glomeruli Research Articles

Increased phosphorylation of focal adhesion kinase in diabetic rat kidney glomeruli

Altered extracellular matrix production by the glomerular mesangium is a feature of diabetes mellitus. Matrix proteins, including fibronectin, via interaction with cell-surface receptors (the integrins) may activate intracellular pathways such as prostaglandin production, shown previously to be stimulated by addition of fibronectin to glomerular cores. However, the signalling pathways involved are unclear. An intracellular tyrosine kinase (focal adhesion kinase), associated with focal adhesions, is known to be phosphorylated after interaction with matrix proteins. We now show for the first time, in glomeruli from diabetic rats, that focal adhesion kinase has increased phosphorylation on tyrosine, when compared with non-diabetic control rats. This phosphorylation was labile and disappeared with extended time of sample preparation or digestion of glomeruli to glomerular cores. Cultured mesangial cells, from non-diabetic rats, plated onto fibronectin also showed increased tyrosine phosphorylation of focal adhesion kinase accompanied by a twofold increase in prostaglandin production. However, it may not be possible to replicate fully the diabetic “state” in vitro merely by use of raised glucose concentrations, as these conditions (for 3 weeks) resulted in decreased focal adhesion kinase phosphorylation, despite increased fibronectin and prostaglandin levels. A role for increased focal adhesion kinase phosphorylation in kidney glomeruli isolated from diabetic rats, and any linkage to intracellular signalling pathways remains to be determined.

EFFECTS ON BINDING CHARACTERISTICS AND RENAL FUNCTION OF THE NOVEL, NON-PEPTIDE ANGIOTENSIN II ANTAGONIST BIBR 277 IN THE RAT

To characterize the interaction of BIBR277, a new angiotensin II (Ang II) type 1 receptor (AT1)-selective antagonist, with rat renal Ang II receptors and to investigate its effects on renal function in vitro and in vivo. The binding characteristics of BIBR277 in the rat kidney were evaluated in [125I]-Ang II displacement and autoradiographic studies. Renal function was assessed in vitro in the isolated, constant-pressure perfused rat kidney and in vivo in anaesthetized rats. In rat kidney cortical membrane preparations BIBR277 binds to a single population of Ang II receptors, which are of the AT1 subtype. In autoradiographic studies specific [125I]-(Sar1,Ile8)-Ang II binding to the rat kidney glomeruli, renal cortex and medulla was completely inhibited by 1 mumol/l BIBR277. In isolated rat kidneys BIBR277 (0.01, 0.1 and 1 mumol/l) increased perfusate flow, urinary flow and glomerular filtration rate concentration-dependently by 115, 130 and 112% of the control value, respectively. This effect was not blocked in the presence of indomethacin (10 mumol/l). Frusemide (10 mumol/l) increased urinary flow in the isolated kidney to about 140% of the control value. The diuretic effect of frusemide was significantly increased to 180 and 200% of the control value in the presence of 0.1 and 1.0 mumol/l BIBR277, respectively. Captopril (10 mumol/l) had no effect on perfusate flow, urinary flow or glomerular filtration rate, and did not increase frusemide-induced diuresis in this preparation. BIBR277 was also administered intravenously to anaesthetized rats at doses of 0.1, 0.3 and 1 mg/kg. BIBR277 had no effect on the heart rate, but decreased the blood pressure significantly at both higher doses. At the 0.3 mg/kg dose, the urinary flow and sodium excretion increased significantly (twofold and 2.47-fold, respectively) compared with the vehicle-treated group, but not increase in the urinary flow and sodium excretion was observed at the highest dose. Urinary potassium excretion was not significantly affected at all doses. These results show that BIBR277 potently interacts with rat renal AT1 receptors. BIBR277 shows diuretic effects both in vitro and in vivo. In anaesthetized rats BIBR277 also promotes sodium excretion without affecting potassium excretion.

Anionic charge concentration of rat kidney glomeruli and glomerular basement membrane.

Estimates of levels of glomerular and glomerular-basement-membrane anion charge should serve as useful quantitative markers for the integrity of the tissues in health and disease. We have developed a simple, rapid, technique to measure this charge through the use of ion exchange with radioisotopes 22Na+ and 36Cl- at low ionic strengths in phosphate buffer. When this technique is used, normal glomeruli isolated from rat have a measured net anion charge concentration of 17.4 +/- 3.7 p-equiv. per glomerulus (n = 20). Perfused rat kidneys that lose approximately half of their glomerular heparan [35S]sulphate content (owing to oxygen-radical damage) exhibited a lower anion charge, of 7.5 +/- 1.6 p-equiv. per glomerulus (n = 5). Glomerular basement membranes prepared from rat glomeruli by a sonication-centrifugation procedure in the presence of enzyme inhibitors had a charge concentration of 6.3 +/- 0.7 mu-equiv./g wet wt. of tissue (n = 4), whereas membranes prepared by sonication, centrifugation, DNAse and detergent treatment had a charge concentration of 7.1 +/- 1.6 mu-equiv./g wet wt. (n = 4). Isotope-dilution experiments with 3H2O on these detergent-prepared glomerular basement membranes demonstrated that they had a water content of approx. 93%, which would then give a net anion charge concentration of 7.6 +/- 1.7 m-equiv./l (n = 4). These values are in good agreement with those obtained by others using titration techniques [Bray and Robinson (1984) Kidney Int. 25, 527-533]. The relatively low magnitude of glomerular anion charge in normal kidneys is consistent with other recent findings that glomerular anion charge is too low to affect the glomerular transport of charged molecules in a direct, passive, biophysical manner through electrostatic interactions.

Characterization of [3H]SK&F 108566 as a Radioligand for Angiotensin Type-1 Receptor

Rat aortic smooth muscle cells were used as a model system to characterize the binding properties of [3H]SK&F 108566, an angiotensin type-1 (AT1) receptor antagonist. The binding was specific, saturable and reversible. The association and dissociation rates of [3H]SK&F 108566 binding to smooth muscle cells were monophasic and Scatchard analysis of equilibrium binding data yielded a linear plot indicating a homogenous population of binding sites. The maximum binding (Bmax) and apparent dissociation constant (Kd) were 22,000 +/- 6000 sites/cell and 0.83 +/- 0.08nM respectively. The pharmacological specificity of [3H]SK&F 108566 binding to smooth muscle cells is consistent with that observed for AT1 and confirms AT1 receptor specificity of this radioligand. High affinity binding was observed in membranes prepared from bovine adrenal cortex, rat liver and rat kidney glomeruli. COS cells transfected with cDNA encoding human AT1 angiotensin II receptors also displayed high affinity binding site for [3H]SK&F 108566. No specific binding could be detected on membranes prepared from bovine cerebellum, a tissue rich in the angiotensin type-2 (AT2) receptor. These observations indicate that [3H]SK&F 108566 binds to sites which have pharmacological characteristics of angiotensin II AT1 subtype receptors and can be used as a subtype-selective radioligand to characterize AII receptors in various systems.

Podocytes in glomerulus of rat kidney express a characteristic 44 KD protein.

We describe a new monoclonal antibody (MAb) directed against glomerular visceral epithelial cells (podocytes), generated by immunization with isolated rat kidney glomeruli. In immunoblotting experiments this MAb (IgG1 subclass) reacted with a 44 KD protein. In cryostat sections of normal rat kidney the MAb stained glomerular podocytes; therefore, we called the antigen pp44 (podocyte protein 44 KD). On 0.5-micron cryostat sections the signal could be more precisely ascribed to the podocyte foot processes, whereas the cell bodies appeared virtually unreactive. On ultra-thin frozen sections pp44 was found within the cytoplasm of podocyte foot processes at their origin from their parent processes. The podocyte cell membrane was not labeled. All other parts of the nephron were unreactive. An additional but weaker immunoreaction was found in the arterial endothelium; the endothelia of other vessels (peritubular capillaries, veins) were negative. In human kidney anti-pp44 revealed the same staining pattern as in rat kidney. The expression of pp44 was also studied in newborn rat kidney. The early stages of glomerular development (renal vesicle, S-shaped body) were negative. pp44 first appeared during the capillary loop stage, i.e., when formation of podocyte foot processes commences. In comparing the present results with published data, pp44 is clearly different from other antigens thus far described in podocytes. From the results of this investigation we conclude that pp44 represents a novel cytoplasmic protein of podocytes. Our data suggest a cytoskeletal role for pp44 in preserving the complex architecture of podocytes. This idea is confirmed by the simultaneous appearance of foot processes and anti-pp44 immunoreactivity during glomerular development.

Isolation of a 330-kDa glycoprotein from human kidney similar to the Heymann nephritis autoantigen (gp330).

Because of the similarities between Heymann nephritis of rat and human membranous glomerulonephritis, we searched for a protein in human kidney similar to that of the putative autoantigen of Heymann nephritis, gp330. Human gp330 was isolated by a purification scheme identical to that used for the isolation of rat gp330. The isolated human gp330 was compared with rat gp330 by peptide mapping and was found to be very similar in structure. Studies of immunologic reactivity of the rat antigen-induced Heymann nephritis nephritogenic autoantibody to human gp330 indicated that some of the rat antigen epitopes were shared with its human counterpart. The human gp330 was capable of eliciting on active Heymann nephritis response in rats when used as an immunogen. The nephritogenic autoantibody eluted from these rat kidney glomeruli showed equal binding to both rat and human antigens. Finally, a polyclonal antibody to human gp330 was able to induce passive Heymann nephritis in rats. These results demonstrate that there is a gp330 protein in human kidney that is very similar to the putative autoantigen of Heymann nephritis.

Investigation of the tridimensional ultrastructure of rat glomerular capillary endothelium by high-resolution scanning electron microscopy

The principal applications of scanning electron microscopy (SEM) to renal ultrastructure have been in the study of the surface topography of various kidney cell types and their orientation and distribution in both health and disease. SEM study, however, has been limited in a major way by a lack of resolution sufficient to readily examine in detail and in three dimensions such features as glomerular basement membrane substructure and the structural organization at high magnification of the glomerular, capillary endothelium. Consequently, most of our current information about the 3D ultrastructure of rat kidney glomerulus has been obtained from transmission electron (TEM) micrographs obtained from thin sections cut at various planes followed by computer assisted, serial reconstructions. Recent advances in specimen preparation techniques and scanning electron microscope design have permitted ultrastructural examination of the glomerular capillary wall in three dimensions using high resolution scanning electron microscopy (HRSEM). Specimens in which the cytosol and cytoskeleton have been extracted, but cell membranes nuclear structures and organelles left in place, were studied using a Hitachi SEM with a resolution of approximately 3 nm.

モノカインによるメサンギウム細胞の増殖促進

An involvement of monokines in proliferation of mesangial cells was studied in experimental mesangial cell proliferative glomerulonephritis model and in culture. Anti-rat thyrnocyte serum (ATS) recognized Thy-1.1 (-like) molecules on the glomerular mesangial cells and an intravenous administration of ATS in rats induced glomerular hypercellular lesion 4-7 days later. The glomerular lesion was composed mainly of proliferating mesangial cells as defined by immunofluorescence staining for Thy-1.1 or desmin and less of infiltraing monocytes and lymphocytes as characterized by presence of leucocyte common or Ia antigen.The promotion of mesangial cell proliferation in the glomeruli of ATS-administered rat kidneys was supported by enhancement of 3H thymidine uptake in the glomerular cells in culture and by increase of Thy-1.1 mRNA content in the glomerular RNA. The glomeruli from the ATS-administered rats released interleukin 1 (IL-1) and tumor necrosis factor (TNF) activities in culture medium and had more IL-1β mRNA than control rat glomeruli. Recombinant human IL-1β and TNF enhanced proliferation of quiescent rat mesangial cells in culture in the simultaneous presence of low concentration of fetal bovine serum or platelet-derived growth factor, as was the case with insulin.These results indicate that monocytes/macrophages infiltrating in glomeruli with glomerulonephritis could release monokines, such as IL-1 or TNF and these cytokines could promote proliferation of mesangial cells.

Angiotensin II and bradykinin stimulate phosphoinositide breakdown in intact rat kidney glomeruli but not in proximal tubules: Glomerular response modulated by phorbol ester

We have investigated the effect of angiotensin II, bradykinin, insulin and insulin-like growth factor I on phosphoinositide turnover in intact rat glomeruli and tubules. Angiotensin II produced a dose-dependent increase in inositol monophosphate formation with an IC 50 of 10 −7 M, when added to isolated rat glomeruli. Angiotensin II-stimulated inositol phosphates formation was inhibited by the angiotensin receptor antagonist [Sar-Leu8]angiotensin II, indicating that the above response was mediated through activation of an angiotensin receptor in intact glomeruli. Besides angiotensin, in intact glomeruli, only bradykinin stimulated a phosphoinositide response, while in intact proximal tubules, none of the agonists tested produced an activation of the inositol phosphate formation. Angiotensin II- and bradykinin-stimulated inositol phosphate accumulation in intact glomeruli was inhibited by phorbol myristate acetate, an activator of protein kinase C.

Characterization of renal glomerular endothelin receptors in the rat

Specific receptors for Endothelin (Et) have been identified in the glomerulus of rat kidney. Human 125I-ET binds to a single population of high affinity receptors in glomerular membranes from normal rats with a mean equilibrium dissociation constant of 200 pM. The binding was time and temperature-dependent, saturable and reversible. The Et-receptor complex was not affected by either vasopressin, atrial natriuretic factor or angiotension II.

Autoradiographic localisation of endothelin binding sites in kidney

[ 125I]Endothelin binding sites occurred in glomeruli of human, monkey, rat and dog kidney but not rabbit glomeruli. The renal medulla had more binding sites in all species, with the greatest densities of all in the rat and monkey renal papillas. Binding in rat kidney was inhibited by [Ala 3,11]endothelin with lower potency than endothelin but not by unrelated peptides. These binding sites may represent the endothelin receptors and suggest actions for endothelin on renal function.

In vivo generation of hydrogen peroxide by rat kidney cortex and glomeruli.

The purpose of this study was to demonstrate in vivo generation of hydrogen peroxide by rat renal cortex and glomeruli. Aminotriazole irreversibly inactivates catalase only in the presence of hydrogen peroxide, and previous studies have shown that aminotriazole-mediated inhibition of catalase is a measure of in vivo changes in the hydrogen peroxide generation. Aminotriazole injected intraperitoneally caused a dose-dependent (0.1-1 g/kg) and a time-dependent (15, 30, 60, 90, 120 min) inhibition of the catalase activity in renal cortex. We confirmed that catalase inactivation by aminotriazole was due to formation of a catalase-hydrogen peroxide intermediate (compound I) because catalase inactivation was prevented by ethanol (2 g/kg), a competitive substrate for compound I. The specific activity of catalase in the glomeruli [0.27 +/- 0.026 k/mg protein (where k is the first-order reaction rate constant), n = 5] was significantly lower than the specific activity in the tubules (1.04 +/- 0.15 k/mg protein, n = 5) obtained from the same rats. The residual catalase activity (RCA) in the glomeruli (0.05 +/- 0.01 k/mg protein) was 19% of control values at 90 min after aminotriazole injection (1 g/kg). Taken together these data provide evidence for in vivo generation of hydrogen peroxide by rat renal cortex and glomeruli under normal conditions. Aminotriazole-mediated inhibition of catalase has been used in previous studies as a measure of in vivo changes in the hydrogen peroxide generation.(ABSTRACT TRUNCATED AT 250 WORDS)

Glomerular and Tubular α- and α-Adrenoceptors in the Rat Kidney

Rat kidney glomeruli and cortical tubules were obtained by a combination of sieving and differential centrifugation technique. [3H]Prazosin and [3H]rauwolscine were used to identify and quantify the alpha 1- and alpha 2-adrenergic receptors, respectively. In the glomeruli, the alpha 1-adrenoceptor concentration was 27% and alpha 2-adrenoceptor concentration was 33% of the corresponding values in the tubules. Further localization of the tubular alpha-adrenoceptors was undertaken by studies in the isolated basolateral membrane and comparison with values in the crude plasma membrane. alpha 1-Adrenoceptors were enriched 1.54 +/- 0.1 times and alpha 2-adrenoceptors were enriched 1.73 +/- 0.04 times in the basolateral membrane as compared to crude plasma membrane. However, these values were significantly (p less than 0.05) less than the enrichment value of 2.77 +/- 0.3 obtained for the basolateral membrane marker (Na+ + K+)-ATPase. These results suggested the possibility that alpha 1- and alpha 2-adrenoceptors may also be distributed in the brush border membrane. Direct-binding studies in the purified renal brush border membrane indicated alpha 1-adrenoceptor concentration of 82.1 +/- 3.8 and alpha 2-adrenoceptor concentration of 108.2 +/- 9.3 fmol/mg protein. These values were 32 and 17% of the corresponding values in the basolateral membrane. Overall, our results suggest that alpha 1- and alpha 2-adrenoceptors are present both in the basolateral and brush border membranes analogous to what has been reported for angiotensin and insulin receptors; their primary concentration, however, is in the basolateral membranes.

Beta-adrenergic receptor coupled adenylate cyclase in rat kidney: Differential coupling in glomeruli and tubules

[ 125I]Iodocyanopindolol ([ 125I]ICYP) was used to identify and characterize the β-adrenoceptors in isolated rat kidney glomeruli and cortical tubules. In both the tissues, specific binding of [ 125I]ICYP was saturable with time and ligand concentration and showed appropriate stereospecificity and agonist rank order potency characteristic of binding to β-adrenoceptors. Scatchard analysis revealed that the β-adrenoceptor concentration in the glomeruli (111.1 ± 8.9 fmol/mg protein) was about three times that in the tubules (40.1 ±1.8 nmol/mg protein). The dissociation constants ( K D ) were similar in the two tissues. Both β 1- and β 2-adrenoceptor subtypes were present in the glomeruli and tubules, but the β subtype was predominant, constituting greater than 80% of the total β-adrenoceptors in the two tissues. Isoproterenol was twice as potent in competing for [ 125I]ICYP binding in the tubules as in the glomeruli (P < 0.05). The slope factor (pseudo-Hill coefficient) for the isoproterenol competition curve was 0.74 ± 0.04 in the glomeruli and 0.54 ± 0.02 in the tubules (P < 0.05). The nonmetabolized guanyl nucleotide analogue Gpp(NH)p caused a steepening and a 3-fold shift of the isoproterenol competition curve in both tissues. Isoproterenol-stimulated cAMP accumulation in the glomeruli was only 31% of the value in the tubules. The concentration of isoproterenol producing half-maximal stimulation (EC 50) was 114 ± 13 nM in the glomeruli and 19 ± 3 nM in the tubules (P < 0.05). Gpp(NH)p and forskolin caused a similar increase in cAMP accumulation over basal value in the glomeruli as in the tubules. Overall, our results indicate a decreased efficiency in the interaction between the β-adrenergic agonist hormone, the receptor and the guanine nucleotide regulatory protein in the glomeruli as compared to the tubules.

Glomerular sialoconjugates of developing and mature rat kidneys

The appearance of sialoconjugates in developing rat kidney glomeruli was studied using lectins and neuraminidase-lectin staining sequences. In the early S-shaped bodies, binding of Maclura pomifera (MPA; specific for galactosaminyl residues of glycoconjugates) could be detected in the presumptive podocyte layer at the apex of these cells, but notably no binding of lectins specific for sialic acid could be seen. During further morphologic maturatin of the S-shaped bodies, binding of Limax flavus (LFA; specific for sialic acids) and Triticum vulgaris (WGA; specific for sialic acids and N-acetyl glucosaminyl moieties) appeared at the apex of podocytes and extended subsequently along the lateral membranes to the base of these cells. In morphologically mature glomeruli, LFA stained not only the base of podocytes but also glomerular basement membranes. WGA and MPA bound to the capillary endothelia as well as to the structures bound by LFA. The intensity of WGA binding increased considerably after 5 days of postnatal life, seemingly in parallel with the decrease and ultimate disappearance of MPA binding. In addition to showing individual appearance pattern for various lectin binding sites, these studies give evidence of previously unrecognized postnatal completion of the components of glomerular filtration barrier.

Isolation and characterization of insulin receptors from rat kidney glomeruli and tubules

In order to directly compare the structural characteristics of renal glomerular and tubular insulin receptors, the purified isolated nephron subunits were extracted with 1% Triton X-102, fractionated by DEAE-Sephacel ion exchange column chromatography and the fractions containing insulin binding proteins were identified by the precipitation of 125I-insulin-protein complexes with polyethylene glycol (PEG). The fractions containing insulin binding proteins were pooled, incubated with 125I-insulin and covalently cross-linked with disuccinimidyl suberate, followed by chromatography of the cross-linked samples on Sepharose CL-6B. From both glomeruli and tubules, three 125I-insulin-binding complexes with molecular weights of 560KDa, 220KDa and 95KDa were found. SDS-PAGE of these complexes from glomeruli and tubules under both reducing and nonreducing conditions gave similar patterns of 125I-insulin-crosslinked components, with the exception of the polypeptide pattern from the 560KDa peak fraction which was markedly different between glomeruli and tubules with the former giving major labeled components at 170 and 68KDa while the latter showed labeled components of 125KDa and > 250KDa. Glomerular and tubular insulin receptors, therefore, display similar subunit composition under reducing conditions, but differ in the non-reduced state, suggesting that these complexes may differ in the extent and/or nature of disulfide bonding.

Effect of vasoactive intestinal polypeptide on the cyclic adenosine monophosphate generating system in rat kidney glomeruli and cortical tubules

The effect of in vitro addition of vasoactive intestinal polypeptide (VIP) on the 3′-5′-cyclic adenosine monophosphate (cAMP) generating system in rat kidney glomeruli and cortical tubules was studied. VIP did not stimulate cAMP accumulation in glomeruli; but VIP did stimulate, specifically and in a dose-dependent manner, cAMP concentrations in tubular membranes with the addition of GTP. These results are consistent with the existence of a functionally active VIP receptor coupled to adenylate cyclase in rat kidney cortical tubules.

Insulin binding by isolated rat kidney glomeruli

Conference Article| October 01 1986 Insulin binding by isolated rat kidney glomeruli DAVID MURRAY; DAVID MURRAY 1Division of Biochemistry, St. Thomas's Hospital Medical School (U.M.D.S.). London SE1 7EH, U.K. Search for other works by this author on: This Site PubMed Google Scholar ANTHONY LOPEZ; ANTHONY LOPEZ 1Division of Biochemistry, St. Thomas's Hospital Medical School (U.M.D.S.). London SE1 7EH, U.K. Search for other works by this author on: This Site PubMed Google Scholar PHILIP G. DAVEY; PHILIP G. DAVEY 1Division of Biochemistry, St. Thomas's Hospital Medical School (U.M.D.S.). London SE1 7EH, U.K. Search for other works by this author on: This Site PubMed Google Scholar J. HYWEL THOMAS J. HYWEL THOMAS 1Division of Biochemistry, St. Thomas's Hospital Medical School (U.M.D.S.). London SE1 7EH, U.K. Search for other works by this author on: This Site PubMed Google Scholar Biochem Soc Trans (1986) 14 (5): 975. https://doi.org/10.1042/bst0140975 Article history Received: March 18 1986 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Cite Icon Cite Get Permissions Citation DAVID MURRAY, ANTHONY LOPEZ, PHILIP G. DAVEY, J. HYWEL THOMAS; Insulin binding by isolated rat kidney glomeruli. Biochem Soc Trans 1 October 1986; 14 (5): 975. doi: https://doi.org/10.1042/bst0140975 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Society Transactions Search Advanced Search This content is only available as a PDF. © 1986 Biochemical Society1986 Article PDF first page preview Close Modal You do not currently have access to this content.

A Modified Method of Fine-Granular Cationic Iron Colloid Preparation: Its Use in Light and Electron Microscopic Detection of Anionic Sites in the Rat Kidney Glomerulus and Certain Other Tissues

Ferric chloride, when boiled with hydrazine hydrate and cacodylic acid, is converted into a fine cationic iron (ferric hydroxide) colloid which consists of 0.5-1.5 nm electron-dense granules, and gives a distinct Prussian blue reaction. This colloid allows light and electron microscopic detection of ionized anionic sites in tissues at a wide pH range of 0.8-7.6. It is smaller in size and more stable, and assures longer and greater staining of tissues, especially at low pH levels, than the iron colloid prepared with sodium or ammonium cacodylate by Seno and his associates (1983, 1984, 1985). Some light and electron micrographs of the rat kidney, spleen and other organs stained with our colloid are presented as examples. These micrographs confirm that the glomerular podocyte end-foot surface facing the Bowman's capsular space is strongly negative-charged. They also show that almost all lymphoid cells around the arteries in the splenic white pulp and thymic cortex contain strongly negative-charged nuclei and that the distal convoluted and collecting urinary tubules are more negative-charged than the proximal convoluted tubules.

Amino acids release somatostatin-like immunoreactivity from isolated rat glomeruli

We reported recently the presence of somatostatin-like immunoreactivity (SLI) in the glomerulus of rat kidney. In the present study, we examined factors affecting SLI release from isolated rat glomeruli using a perifusion system. Perifusate containing a mixture of essential amino acids stimulated SLI release, while other hormonal agents such as parathyroid hormone, vasopressin, angiotensin II, bradykinin, epinephrine, PGE 2, known to have direct actions on the glomerulus, had no discernible effect on SLI release. Addition of somatostatin to the perifusate did not affect either basal or angiotensin II-stimulated PGE 2 release from isolated glomeruli. Our preliminary results demonstrate the stimulatory effect of mixed amino acids on somatostatin release from isolated glomeruli. Further studies are needed to elucidate the possible physiological significance of the present findings.