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D Chansel

Publications and source records attributed to D Chansel.

At least 37 records · Page 2Linked to original sources
PubMed1992

Characterization of angiotensin II receptor subtypes in human glomeruli and mesangial cells.

This study was designed to identify the subtypes of angiotensin II (ANG II) receptors present on glomeruli and glomerular mesangial cells and establish their functional significance. Dup 753 and its metabolite EXP 3174, two nonpeptide ANG II-1 receptor (AT1) antagonists, displaced 125I-ANG II and its analogue 125I-[Sar1,Ala8]ANG II from their binding sites in rat and human glomeruli and cultured human mesangial cells, whereas CGP 42112 A and PD 123177, two ANG II-2 receptor (AT2) antagonists, exhibited little displacing activity. Dup 753 and EXP 3174 did not modify the dissociation constant (Kd) value but markedly decreased the number of sites of 125I-[Sar1,Ala8]ANG II binding. The addition of PD 123177 did not further inhibit binding when all AT1 sites were occupied by Dup 753. Binding was markedly reduced by dithiothreitol. EXP 3174 and Dup 753 inhibited the main biological functions of ANG II in mesangial cells including increases in intracellular calcium concentration, PGE2 production, and protein synthesis. PD 123177 was also active but at concentrations 1,000- to 10,000-fold greater than those of AT1 antagonists. These results indicate that 1) only AT1 receptors are present in glomeruli and glomerular mesangial cells; 2) these receptors mediate the functional responses to ANG II; 3) the nonpeptide AT1 antagonists behave as noncompetitive inhibitors; and 4) high concentrations of the nonpeptide AT2 antagonists can recognize AT1 sites.

Angiotensin II↗
PubMed1992

Cell surface receptors and ectoenzymes in mesangial cells.

Mesangial cells possess a variety of receptors for hormones and autacoids. They are also equipped with ectoenzymes whose function may be to control the availability of autacoids and hormones at their receptor sites. Several examples are considered. Receptors for angiotensin II (AII) are present both on murine and human mesangial cells. One single group of receptors has been demonstrated in each of these preparations. Mesangial cell AII receptors are linked to phospholipase C via a G protein. They belong to the AT1 subtype because (125I)AII is displaced from its binding sites preferentially by AT1 antagonists such as DUP 753 and EXP 3,174, whereas AT2 antagonists are much less potent. AT1 antagonists suppress the biological effects of AII in mesangial cells, including the stimulation of intracellular calcium concentration and the increase of prostaglandin synthesis and of (3H)leucine incorporation. Mesangial cells also have receptors for atrial natriuretic factor, but the distribution between B receptors with guanylate cyclase activity and clearance (C) receptors varies with the species. Both types are present in murine mesangial cells, whereas only C receptors are found in human mesangial cells. In contrast, human epithelial cells possess both B and C receptors. Ecto-5'-nucleotidase activity results in the production of adenosine, which acts on mesangial cells through A1 and A2 receptors. This enzyme is markedly induced in rat mesangial cells by interleukin-1, whose effect is mediated in part by prostaglandin E2 and cAMP. Various other cAMP-stimulating agents also induce 5'-nucleotidase expression in rat mesangial cells. Ectopeptidases are present in all glomerular cell types but essentially in epithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)

5'-Nucleotidase↗
PubMed1992

[Mechanism of action and catabolism of atrial natriuretic factor in cultured human and animal kidney cells].

Cultures of renal cells from human or animal origins have allowed the modes of action and the degradation pathways of atrial natriuretic factor (ANF) to be characterized. Human glomerular mesangial and epithelial cells possess ANF receptors of both types, only clearance receptors (C) in mesangial cells, receptors with guanylate cyclase activity (A) and C receptors in epithelial cells which are, in addition, equipped with ectoenzymes rapidly degrading extracellular ANF. Epithelial cells which have been stimulated by ANF secrete cyclic guanosine monophosphate (cGMP) at their apical side. Vascular smooth muscle cells prepared from the rabbit renal cortex also possess A receptors of high affinity and C receptors. Neutral endopeptidase (NEP), an enzyme of which ANF is a specific substrate in the kidney, is expressed at the cell surface. Its expression is inhibited by factors present in the serum and is increased by glucocorticoids. Principal cells of the collecting duct are also a target for ANF via A and C receptors. Taken together, these studies demonstrate that the kidneys are sites both for the physiological effects and the degradation of ANF. Production of cGMP results in vasodilation in the renal cortex, increase of glomerular filtration rate and decrease of sodium reabsorption in the collecting duct. Degradation of ANF occurs via two different ways, its conversion into inactive peptides by NEP and its internalization after binding to C receptors.

Animals↗
PubMed1990

Characterization of atrial natriuretic factor receptors in human glomerular epithelial and mesangial cells.

To evaluate the distribution and functions of receptors of atrial natriuretic factor (ANF) in human glomeruli, we studied the binding sites of ANF-(1-28) in homogeneous populations of human glomerular epithelial cells or mesangial cells. 125I-labeled ANF bound specifically to both cell types. Equilibrium saturation binding curves suggested one group of receptor sites in mesangial cells (Kd = 99 +/- 32 pmol/l, Bmax = 15.3 +/- 3.5 fmol/mg) but multiple groups in glomerular epithelial cells. Binding was greater at 37 than at 4 degrees C in mesangial cells. The reverse was observed in glomerular epithelial cells due to marked degradation of the tracer at 37 degrees C. The fractions of undisplaceable tracer in a hypertonic acid medium after 60 min incubation were 45 and 16% at 37 degrees C for glomerular epithelial and mesangial cells, respectively. ANF-(1-28) and C-ANF-(4-23), a specific ligand of clearance receptors, similarly inhibited 125I-ANF binding to mesangial cells, whereas [Ala7-Ala23]-ANF, a linear analogue, was slightly less potent. In epithelial cells, C-ANF-(4-23) competitively inhibited 125I-ANF binding but with a lower potency than ANF, whereas linear ANF at low concentrations (10-100 pmol/l) stimulated 125I-ANF binding. In addition, linear ANF markedly inhibited the degradation of 125I-ANF in the incubation medium of epithelial and mesangial cells, whereas thiorphan, an inhibitor of enkephalinase, was inactive. ANF-(1-28) stimulated cGMP production in glomerular epithelial cells but not in mesangial cells. Both analogues were inactive in both cell types and did not modify ANF-(1-28)-dependent cGMP synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Natriuretic Factor↗
PubMed1989

Effects of bradykinin on prostaglandin synthesis and cytosolic calcium in rabbit subcultured renal cortical smooth muscle cells.

Smooth muscle cells were cultured from an arteriole-rich fraction of the rabbit renal cortex and characterized by their ultrastructural and immunohistochemical features, their high content in creatine kinase (60-times that of the initial preparation) and their ability to synthesize renin. Cells, studied between passages 2 and 5, produced mainly PGE2 and, to a lesser extent, PGF2 alpha. Bradykinin (BK) (0.1 nM-1 microM) induced a concentration-dependent increase in PGE2 (28-40-times basal value at 1 microM after a 5 min incubation period) and stimulated also the free cytosolic calcium concentration [( Ca2+]i) with a 2-fold maximal rise to its basal value. Both effects, inhibited by the anti-B2 receptor [Thi5.8D-Phe7] BK, were not reproduced by DesArg9 BK. A decrease in the extracellular calcium concentration and incubation in the presence of a calcium-channel blocker (lanthanum chloride) inhibited the BK-dependent rise of [Ca2+]i but not that of PGE2. Preincubation with phorbol myristate acetate increased basal and BK-induced PGE2 synthesis but prevented the effect of BK on [Ca2+]i. These results demonstrate the ability of BK to increase [Ca2+]i and PGE2 production in cultured vascular cells from the rabbit renal cortex and suggest that kinins might act on the cortical microcirculation via their direct effects on arteriolar smooth muscle cells.

Animals↗
PubMed1989

Modulation of renin synthesis by lipoxygenase products in cultured human mesangial cells.

Modulation of renin synthesis by lipoxygenase products has been studied in cultured human mesangial cells under basal conditions and in the presence of prostaglandin (PG) E2. Total renin and cyclic AMP productions were stimulated in a dose-dependent manner (0.1-10 microM) by PGE2. The stimulatory effect of PGE2 on renin production was inhibited by 12-hydroxyeicosatetraenoic acid (12-HETE) between 0.1 and 100 nM. Extracellular and intracellular renin were affected similarly. Neither basal and PGE2-dependent cyclic AMP nor basal cyclic GMP productions were modified. 15-Hydroxyeicosatetraenoic acid (15-HPETE), 12-hydroperoxyeicosatetraenoic acid (12-HPETE) and 15-hydroperoxyeicosatetraenoic acid (15-HPETE) had the same effects as 12-HETE. Intracellular calcium concentration was not modified in the presence of 12-HETE. Since oleyl-2-acetylglycerol (OAG), an analog of diacylglycerol, also inhibited PGE2-stimulated renin production, it is hypothesized that the effect of the lipoxygenase products is mediated via protein kinase C stimulation.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1987

Angiotensin I-converting enzyme in isolated human glomeruli.

Angiotensin I-converting enzyme (ACE) activity was measured with hippurylhistidylleucine as a substrate in isolated human glomeruli. The mean level was 2.2 +/- 0.47 mIU/mg glomerular protein. S9780, a newly designed competitive inhibitor of ACE, inhibited this activity by 85% at 0.3 microM. [3H]S9780 specifically bound to isolated human glomeruli. The Kd value and the number of sites were 23 nM and 83 fmol/mg, respectively. The prodrug, S9490, and Captopril were less potent than S9780 in displacing [3H]S9780 from its binding sites. Angiotensin I had no effect. Binding of [3H]S9780 was inhibited after preincubation of the glomeruli with a specific polyclonal anti-human ACE antibody. These results demonstrate that ACE is present in human adult glomeruli.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1987

Identification and regulation of renin in human cultured mesangial cells.

Renin activity was measured in the incubation medium, and the cellular extract of human mesangial cells, which had been cultured in the presence of renin-free human plasma (three kidneys; 4-7 passages). Active renin and total renin obtained after trypsin treatment was estimated by radioimmunoassay of angiotensin I using renin-free human plasma as a substrate. Mesangial cell renin had characteristics similar to those of standard human renin; optimum enzymatic activity at pH 5.8, marked inhibition in the presence of two (monoclonal and polyclonal) human renin-specific antibodies and of SR 42128, a new potent statine-containing renin inhibitory peptide. The synthetic capability of the mesangial cells varied markedly with the original kidney (1-49 and 0.3-0.9 ng X h-1 X mg-1 for total renin in the medium and the cellular extract respectively). Renin was secreted mainly as inactive renin. Prostaglandin E2 (PGE2) and carba-prostaglandin I2 (PGI2) (a stable analogue) produced a dose-dependent (0.1-1.10 microM) increase in renin activity in both the cellular extract and the culture medium. Isoproterenol (200 microM) increased renin activity only in the medium. The effects of these agonists were more marked on inactive than on active renin. These results demonstrate that cultured human mesangial cells synthesize and release renin in a stable manner over a long period of culture, thus providing a useful tool for the in vitro study of renin secretion and its control.

Cells, Cultured↗
PubMed1984

Solubilization of angiotensin II receptors in rat glomeruli.

125I-labelled angiotensin II (A II) specifically binds to solubilized receptors extracted from rat isolated glomeruli using CHAPS (3-[3-( cholamidopropyl ) dimethylammonio ]-1-propanesulfonate). The yield of solubilization of the binding sites was 3.3%. Equilibrium was reached after 15-20 min and specific binding represented 75% of total binding. Dissociation of the hormone-receptor complex after addition of an excess of A II was very slow in the presence of Ca2+ and Mg2+. [Sar1 Ala8] A II and [Sar1 Ile8] A II were more potent as competitive inhibitors of 125I-labelled A II than A II itself and its heptapeptide. These basic features of 125I-labelled A II binding to the extracted material were similar to those observed previously with untreated glomeruli.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMed1983

PGE2 binding sites and PG-stimulated cyclic AMP accumulation in rat isolated glomeruli and glomerular cultured cells.

[3H]PGE2 specifically bound to isolated glomeruli. The KD value and the number of sites were 80 nM and 528 fmoles/mg respectively. PGE1 and PGE2 resulted in equipotent inhibition of binding whereas PGI2 was markedly less active. It was not possible to demonstrate specific receptors for PGE2 in glomerular mesangial and epithelial cultured cells. PGE1, PGE2 and PGI2 (0.1-100 microM) stimulated cyclic AMP concentration both in isolated glomeruli and glomerular cultured cells. Basal cyclic AMP in epithelial cells was greater than in mesangial cells or glomeruli. The cyclic AMP accumulation in the presence of PGs was greatest in mesangial cells. Maximum stimulation was in the range 300-1400%. For the three preparations, PGE2 and PGE1 produced a greater effect than PGI2. ED50 values were identical for PGE1 and PGE2 (5 microM for epithelial cells and glomeruli, 20 microM for mesangial cells). ED50 value for PGI2 were lower than those for PGE1 or PGE2 (0.2, 2 and 5 microM for glomeruli, epithelial cells and mesangial cells, respectively). The effects of the three PGs were not additive when tested at maximally effective concentrations. These results demonstrate that PGE1, PGE2 and PGI2 stimulate glomerular and cellular cyclic AMP. A relationship between [3H]PGE2 binding sites and this biological effect has not been established. The physiological events secondary to the increase in glomerular cyclic AMP are also yet to be determined.

Animals↗
PubMed1982

Histamine H2 receptors in rat renal glomeruli.

The aim of this study was to demonstrate histamine-H2 receptors in glomeruli isolated from rat renal cortex and to correlate binding to stimulation by histamine of glomerular cyclic AMP concentration. Binding studies were performed at 10-12 degrees C using [3H]cimetidine as a tracer. Specificity of binding relies on the following: inhibition of [3H]cimetidine binding by the unlabelled drug, other H2-antagonists and agonists in contrast with the very weak inhibitory effects of H1 agonists and antagonists; reversibility of steady-state binding after addition of unlabelled drug; half inhibition of the glomerular cyclic AMP response to histamine at concentrations of cimetidine close to the KD value derived from the binding studies (3 microM); calculated KD value in agreement with the therapeutical concentration of cimetidine and the physiological concentration of histamine. [3H]Cimetidine binding concentration of cimetidine and the physiological concentration of histamine. [3H]Cimetidine binding strikingly increased in the presence of copper chloride (20-300 microM) due to an increase both in number of sites and affinity. However this greater binding did not influence either the inhibitory effect of cimetidine on histamine-induced glomerular cyclic AMP concentration or the stimulatory effect of histamine itself. [3H]Cimetidine binding was temperature-dependent since it progressively diminished from 0 to 37 degrees. This was not due to [3H]cimetidine degradation as shown by thin layer chromatography but rather to a change in drug-receptor interaction at higher temperatures. Glumerular concentration of cyclic AMP increased progressively in the presence of histamine (0.1-1000 microM). This stimulatory effect was markedly inhibited by H2 antagonists. These data demonstrate the presence in rat glomeruli of H2 receptors linked to adenylate cyclase.

Animals↗
PubMed1982

Angiotensin II receptors in human isolated renal glomeruli.

125I-Labeled angiotensin II ([125I]A II) binds specifically to glomeruli isolated from human kidneys that were obtained at nephrectomy or early autopsy. Equilibrium was reached after 30 min, and specific binding represented more than 90% of the total binding. Dissociation after dilution with the addition of an excess of unlabeled hormone was more rapid than after dilution alone. The effect increased as a function of the A II concentration. The Scatchard plot derived from saturation experiments was curvilinear, with an upward concavity. Two groups of receptor sites could be defined by the Kd values (0.1 and 2 nM, respectively) and the number of receptor sites (40 and 300 fmol mg glomerular protein-1, respectively). Alternatively, binding could be considered to follow a negative cooperative type of hormone-receptor interaction. [Asn1, Val5]A II, [Asp1,Ile5]A II, [des, Asp1,Ile5]A II, [Sar1, Ala8]A II, and [Sar1, Ile8]A II were all equally effective as competitive inhibitors of [125I]A II binding. Both calcium and magnesium (0.5-5 mM) produced an increase in [125I]A II specific binding, whereas guanylylimidodiphosphate, an analog of GTP, inhibited it. Degradation of the [125I]A II present in the incubation medium was estimated by three different techniques. It increased linearly with time and reached 20% at 30 min. Specific binding of A II to human glomeruli at plasma concentrations observed in man under physiological conditions and during the iv administration of A II demonstrates that human renal glomeruli include target cells for A II and thus suggests a role for A II in regulation of the glomerular filtration rate in man.

Adult↗
PubMed1981

Stimulation by oxygen radicals of prostaglandin production by rat renal glomeruli.

Polymorphonuclear leukocytes secreting oxygen radicals are found in the glomerular capillaries at an early stage of experimental acute glomerulonephritis. The aim of this work was to study the effects of these radicals on prostaglandin (PG) production by the glomeruli. Glomeruli were isolated from rat renal cortex and incubated in the presence of a biochemical system capable of generating oxygen radicals (addition to 100 microM xanthine of increasing concentrations of xanthine oxidase). Synthesis of PGE2, PGF2alpha, 6 keto PGF1alpha, and TXB2 estimated using specific radioimmunoassays was twofold greater in the presence of oxygen radicals. This effect was inhibited by catalase, slightly stimulated by superoxide dismutase, unaffected by hydroxyl radical scavengers, thus suggesting that hydrogen peroxide was the by-product responsible. This was confirmed by the stimulatory effect of hydrogen peroxide itself (1 to 100 microM) on PG synthesis. The effect of mepacrine, an inhibitor of phospholipase activity, on PG production was more marked in the presence of hydrogen peroxide and the stimulation of PG synthesis by hydrogen peroxide or oxygen radicals was progressively inhibited in the presence of arachidonic acid. Moreover, oxygen radicals stimulated the release of 14C-arachidonic acid previously incorporated in isolated glomeruli. This demonstrates that the increase in PG synthesis in response to oxygen radicals is due to activation of glomerular phospholipase by these radicals. This effect that is likely to occur at an early stage of experimental glomerulonephritis could play a role in the mechanism of the inflammatory process.

Animals↗
PubMed1979

Prostaglandin synthesis by isolated rat renal glomeruli.

The PGE2, PGF2 alpha and 6-keto-PGF1 alpha contents of the incubation medium of glomeruli isolated from rat kidney were measured at different times with or without addition of arachidonic acid. These prostaglandins accumulated progressively with time and reached equilibrium after 60--120 min incubation. Synthesis of the 3 prostaglandins was inhibited when indomethacin was added whereas it was markedly enhanced, mainly for PGE2, at increasing doses of arachidonic acid. Plateaus were reached above 5 micrograms/ml and concentrations corresponding to 50% of the maximum values were 2 micrograms/ml for PGE2 and PGF2 alpha, and 0.8 microgram/ml for 6-keto-PGF1 alpha. There were strictly linear relationships between PGE2 or PGF2 alpha productions and the concentration of glomerular protein. PGE2 and PGF2 alpha synthesis with or without arachidonic acid were maximum at 30--37 degrees C. PGE2 glomerular content was almost undetectable initially and increased with time. These data demonstrate that PGE2, PGF2 alpha and PGI2, in order of decreasing abundance, are synthesized by the glomerular cells and suggest that PGE2 and PGI2-sensitive glomerular adenylate cyclase activities and PGE2-sensitive renin synthesis may be stimulated by prostaglandins formed in the glomeruli themselves.

Animals↗