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J Genest

Publications and source records attributed to J Genest.

At least 217 records · Page 12Linked to original sources
PubMed1985

Atrial natriuretic factor inhibits Ca(2+)-dependent K+ fluxes in cultured vascular smooth muscle cells.

The interaction of the synthetic fragment Arg101-Tyr126 of atrial natriuretic factor (ANF) with Ca(2+)-dependent K+ efflux was studied in the following six different cell models: cultured vascular smooth muscle cells from rat aorta; isolated rat glomeruli; human platelets; cultured endothelial cells from bovine aorta; peritoneal mouse macrophages; human red cells. In human red cells and mouse macrophages, the dose-response curves of K+ efflux as a function of Ca2+ ionophore, A23187, concentration were not modified by addition of ANF. In endothelial cells and platelets, ANF slightly inhibited Ca(2+)-dependent K+ efflux. In renal glomeruli, ANF inhibits about one-third of this flux and in vascular smooth muscle cells ANF induced a five- to tenfold increase in the EC50 of A23187 effect. In experiments performed at constant concentrations of A23187, the IC50 of ANF was approximately 10(-9) mol/l. Similar results were obtained in mouse macrophages with cyclic GMP (cGMP). Our results suggest that ANF is able to counterbalance an increase in cytosolic free Ca2+ content in vascular smooth muscle and some glomerular cells. This effect may result from the ability of this hormone to stimulate cGMP synthesis.

Animals↗
PubMed1985

On the circulating form of atrial natriuretic factor.

Isolation and sequencing of IR-ANF from plasma reveal that the circulating form of ANF is a 28-amino acid peptide (Ser 99-Tyr 126) which inhibits basal aldosterone secretion from suspensions of rat zona glomerulosa cells to the same extent as synthetic Arg 101-Tyr 126. The same form (minus two N-terminal amino acids) (Arg 101-Tyr 126) has been isolated from culture media of atrial cardiocytes and sequenced. Structure activity studies of shorter, N- or C-terminally truncated versions of synthetic Arg 101-Tyr 126 show that the latter is the most potent one.

Amino Acid Sequence↗
PubMed1985

Effect of enalapril on renin, angiotensin converting enzyme activity, aldosterone and prostaglandins in patients with hypertension.

Enalapril (MK-421) was administered orally as a single dose of 2.5, 5.0, 10 and 20 mg to 13 patients with either essential or renovascular hypertension. At these doses, enalapril produced a moderate reduction in both supine and standing blood pressure as well as a significant reduction in angiotensin I-converting enzyme activity, an increase in peripheral plasma renin activity and a decrease in plasma aldosterone concentration 4 to 8 hours after administration of the drug. Plasma levels of prostaglandins E1 and E2 were unchanged. The calculated ratio of urinary Na/K was increased in the patients with renal artery stenosis after enalapril. Creatinine clearance was increased in the patients with essential hypertension and reduced in the patients with renal artery stenosis. No adverse effects occurred in these patients treated with single doses of enalapril.

Adult↗
PubMed1985

[The heart, an endocrine gland].

Two independent series of biomedical investigations have led to the discovery that the atria are a peptide-secreting endocrine gland. The first is mainly morphological and starts with the finding that mammalian atrial but not ventricular cardiocytes contain "dense bodies". These "dense bodies" later called "specific granules" were found to be different from lysosomes, to be made up of proteins and to incorporate both 3H-leucine and 3-H-fucose in a pattern typical of peptide-secreting endocrine cells. The finding that rat atrial granulation varied with the sodium and water balance led to the crucial observation that atrial extracts have natriuretic and diuretic effects. In less than 4 years, this new natriuretic hormone has been purified, sequenced and synthetized, and its cDNA and gene have been cloned. The ANF gene has been assigned to the distal short arm of chromosome 1 in band 1P36 while the mouse gene is localized in chromosome 4. The native and synthetic hormones exert identical wide ranging effects (possibly through particulate guanylate cyclase stimulation and adenylate cyclase inhibition) on the kidney, blood vessels, adrenal cortex and pituitary. Physiopathologic implications of the hormone in experimental hypertension, congestive heart failure and expansion of blood volume are already beginning to emerge. On the other hand, the search for natriuretic hormones or factors by studies of negative pressure breathing, atrial distention experiments, head-out water immersion, expansion of blood volume, Na+/K-ATPase inhibition and parabiosis experiments in Dahl rats has provided a general framework within which to interpret this new cardiac function.

Adrenal Cortex↗
PubMed1985

Solid-phase radioimmunoassay for relaxin.

A specific radioimmunoassay (RIA) for porcine relaxin is described in the present report, which also discusses its characterization in terms of its specificity and cross-reactivity to human and rat relaxin. The antibodies used in this assay were developed in rabbits immunized against highly-purified porcine relaxin. They were adsorbed on polystyrene tubes via incubation of a 1:40,000 antibody dilution for 24 hours. NIH relaxin was utilized for iodination by the Bolton-Hunter method and for the standard curve. The RIA was sensitive from 31.3 to 8,000 pg/tube of the porcine hormone. Rat relaxin cross-reacts with the anti-body, but the displacement curve produced by purified rat relaxin was shifted to the right by two orders of magnitude when compared to porcine relaxin. Displacement of 125I-porcine relaxin was also observed with the plasma of pregnant rat or woman, but about 100 times more plasma of these two species was required to produce the same displacement. No cross-reactivity was observed with human, bovine and porcine insulins. This RIA for relaxin will permit clinical evaluation of plasma relaxin concentrations during gestation and in different associated diseases. The concentrations of relaxin in human plasma obtained by this method might represent only a fraction of the actual concentration of the hormone due to low cross-reactivity of the anti-porcine relaxin with human hormone. It is also possible that relaxin is present in lower concentration in the plasma of pregnant woman in comparison to pregnant sow plasma.

Animals↗
PubMed1984

Structure-activity relationships of atrial natriuretic factor (ANF). I. Natriuretic activity and relaxation of intestinal smooth muscle.

Atrial natriuretic factor-related peptides were produced from synthetic ANF (101-126) either by chemical hydrolysis at the N-terminal end or by treatment with carboxypeptidases at the C-terminal end. The biological activities of these peptides were characterized in vivo by a natriuretic bioassay and in vitro by relaxation of contracted intestinal smooth muscle (chick rectum). In the natriuretic assay, the removal of Asn122, Ser123 and Phe124 at the C-terminal end alters considerably the renal response. Deletion or extension of amino acids at the N-terminal end affects only slightly the natriuretic activity. Removal of N-terminal or C-terminal amino acids decreases the relaxant activity of ANF on the chick rectum. In both bioassays, simultaneous deletions of residues at both ends drastically affect the activity in an additive manner.

Amino Acid Sequence↗
PubMed1984

Characterization of specific receptors for atrial natriuretic factor in bovine adrenal zona glomerulosa.

We have recently shown that synthetic rat atrial natriuretic factor (ANF) directly inhibits mineralocorticoid and glucocorticoid secretion in cultured bovine adrenal cells with a potency of 100 pM. [125I]iodo-ANF was used in the present study to characterize potential receptor sites in bovine zona glomerulosa membranes. ANF binds to a class of high affinity binding sites with a pK of 10.2 and a density of 1.3 pmol/mg protein. Detailed competition curves with ANF document a class of high affinity sites with a pK of 10.2 and also a second class of lower affinity sites with a pK of 8.5. Nonspecific binding amounts to less than 10% of [125I]iodo-ANF binding at concentrations less than 100 pM. High affinity binding of [125I]iodo-ANF is reversible with a half-time of association of 15 minutes at 25 pM and a half-time of dissociation of 140 minutes. Monovalent cations Na, Li and K equipotently enhance [125I]iodo-ANF specific binding. Divalent cations Mg, Ca and Mn also increase [125I]iodo-ANF specific binding, with Mn being the most active cation. No effect of guanine nucleotide could be detected on ANF binding. The binding of [125I]iodo-ANF is very specific and is not inhibited by 1 microM angiotensin II, ACTH, VIP, somatostatin, Leu-enkephalin, dynorphin or by the N-terminal of POMC. The N-terminal fragment ANF-(1-16) is also completely inactive. Reduction of the disulfide bridge of ANF inactivates the peptide. This enabled the development of a highly specific radio-receptor assay for ANF with a minimum detectable dose of 2 femtomoles. The results document the specific receptor involved in the potent inhibitory effect of ANF on adrenal steroidogenesis and indicate that bovine adrenal zonal glomerulosa provide a highly sensitive system for studying the recently discovered atrial natriuretic factor.

Adrenal Glands↗
PubMed1984

Atrial natriuretic factor is a circulating hormone.

The radioimmunoassay of atrial natriuretic factor (ANF) has been applied for determination of immunoreactive ANF (IR-ANF) in rat plasma. Immunoreactive ANF has been extracted from rat plasma by immunoaffinity column on Sepharose-4B anti-ANF or by Vycor glass. The mean concentrations of IR-ANF in ether anesthetized rats were found to be 1.61 +/- 0.14 ng/ml in female and 1.25 +/- 0.21 ng/ml in male rats when extracted on Sepharose-4B anti-ANF, and 1.21 +/- 0.10 ng/ml in females and 1.02 +/- 0.11 ng/ml in males when extracted by Vycor glass. A close linear correlation has been observed between the plasma IR-ANF concentrations in aorta and jugular vein. The described results indicate that atrial cardiocytes secrete atrial natriuretic factor into plasma. The heart is, therefore, an endocrine organ.

Animals↗
PubMed1984

Effect of native and synthetic atrial natriuretic factor on cyclic GMP.

Mammalian atrial cardiocyte granules contain a potent natriuretic and diuretic peptide. Since cGMP appears to be involved in the modulation of cholinergic and toxin-induced sodium transport, we examined the effect of atrial natriuretic factor (ANF) on this nucleotide. Atrial but not ventricular extracts elicited approximately a 28-fold increase of urinary cGMP excretion parallel to the natriuresis and diuresis. The atrial extracts also elevated cGMP levels in kidney slices and primary cultures of renal tubular cells. The effect of ANF on cGMP appeared to be specific since antibodies which were capable of inhibiting the ANF-induced diuresis also suppressed cGMP excretion. Furthermore, during the course of ANF purification, the ANF-induced increase of cGMP production by kidney cells paralleled the heightened specific natriuretic activity of the atrial factor. A synthetic peptide (8-33)-ANF similarly increased urinary plasma and kidney tubular cGMP levels. The exact mechanism of action of ANF on cGMP remains to be elucidated, but indirect inhibition of cGMP phosphodiesterase appears to participate in its effect.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1984

Direct radioimmunoassay of atrial natriuretic factor.

A direct radioimmunoassay of atrial natriuretic factor (ANF) has been developed. The method uses a synthetic 26 amino-acid fragment (8-33 ANF) of the native peptide. Antibodies have been prepared in rabbits immunized with the peptide coupled to thyroglobulin. The radiolabelled tracer prepared by iodination according to the Chloramine-T method has been purified by HPLC followed by affinity chromatography on Sepharose-4B anti-ANF. Dextran-coated charcoal has been used for separation of free from antibody bound radioactivity. Higher ANF content has been found in the right rat atrium than in the left. These results have been confirmed by bioassay.

Animals↗
PubMed1984

Atrial natriuretic factor inhibits adenylate cyclase activity.

The synthetic atrial natriuretic factor (ANF) (8- 33AA ) inhibited adenylate cyclase activity in aorta washed particles, mesenteric artery, and renal artery homogenates in a concentration dependent manner with an apparent Ki between 0.1 to 1nM . The extent of inhibition of adenylate cyclase by ANF varied from tissue to tissue. The adenylate cyclase from mesenteric artery and renal artery was inhibited to a greater extent as compared to that from aorta. ANF was also able to inhibit the stimulatory effects of hormones on adenylate cyclase activity and of agents such as F- and forskolin which activate adenylate cyclase by receptor- independent mechanism. In addition, ANF showed an additive effect with the inhibitory response of angiotensin II on adenylate cyclase from rat aorta. These studies for the first time demonstrate that ANF is an inhibitor of adenylate cyclase of several systems.

Adenylyl Cyclase Inhibitors↗
PubMed1984

Atrial pronatriodilatin: a precursor for natriuretic factor and cardiodilatin. Amino acid sequence evidence.

Numerous peptides isolated from rat heart atria, including two containing 33 and 73 amino acids, were isolated and shown to exhibit natriuretic activities. Here, we describe the purification and partial amino acid sequence of a 106-residue peptide containing the previously sequenced 33- and 73-amino-acid ANF peptides. The determined sequence is a novel one and is not significantly homologous to any known protein or segment thereof. In fact, this sequence shows significant homology only to another novel partial sequence obtained from sequence analysis of a porcine peptide, called cardiodilatin, also found in heart atria. This relationship is taken as evidence that ANF and cardiodilatin are part of the same precursor molecule which would contain at the very least 126 amino acids.

Amino Acid Sequence↗
PubMed1984

Comparative vasoactive effects of native and synthetic atrial natriuretic factor (ANF).

The presence of a natriuretic factor in mammals atria has been confirmed by many laboratories. In addition to its natriuretic and diuretic activities, atrial preparation of uncertain degree of purification are known to contain a vasoactive substance. By the use of pure atrial natriuretic factor of known amino acid sequence and its synthetic homologue we have presented strong evidences suggesting that natriuretic and vasoactive activities are indeed mediated by the same peptide. As this peptide has not yet been detected in the circulation, its actual physiological relevance remains to be elucidated.

Animals↗
PubMed1984

Primary structure of a high Mr form of rat atrial natriuretic factor.

During the purification of rat atrial natriuretic factor (ANF), low, intermediate and high Mr forms were observed. In this report we describe the purification and amino acid sequence of a 73 residue peptide containing at its C-terminus the previously sequenced 33 amino acid ANF peptide. The cleavage necessary to produce the 33 amino acid ANF from the 73 amino acid precursor occurs at a Leu-Leu bond. We also report the amino acid composition of an even longer form of ANF containing about 103 residues, in which the extension is amino terminal to the 73 peptide. A computer data bank search showed that the determined sequence is a novel one and is not homologous to any known proteins or segment thereof. The natriuretic activity of the 73 amino acid form when compared to that of a synthetic ANF peptide, comprising the sequence of the last 26 amino acids of ANF, was found to be slightly lower.

Amino Acid Sequence↗