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Biomedical subjects

R K Hindawi

Publications and source records attributed to R K Hindawi.

7 recordsLinked to original sources
PubMed1990

Reduced levels of PGE2 uptake by intact reno-medullary collecting tubule cells isolated from the spontaneously hypertensive rat and the identification of an intracellular PGE2 receptor/binding protein.

Prostaglandin E2 (PGE2) is thought to be involved in the control of NaCl loading in the kidney. Since the ability to balance salt concentrations across the nephron appears to be impaired in the Spontaneously Hypertensive Rat (SHR), the uptakes of PGE by isolated medullary collecting tubule cells (MCT) from both SH and normotensive (NT) rats were compared. A rabbit antiserum directed against PGE2 revealed by flow cytometry the active internalisation of exogenous ligand by a high density fraction of intact MCT cells from NT tissue. Conversely, PGE2 uptake by the same fraction was markedly reduced. The monoclonal antibodies (MoAbs) W2.44 and SH6.6 raised against a 45,000 X g fraction of medullary tissue and which blocked binding of the anti-PGE2 serum, identified by Western blotting, an intracellular PGE2 receptor or binding protein (PGER) of 16 k daltons. No alteration in the structure or level of expression of this antigen could be detected in the MCT fractions isolated from the SHR. It is suggested that an impairment of PGE2 membrane transport in the renal medulla may be a contributory factor to the SH condition.

Animals↗
PubMed1985

The role of prostaglandins in aldosterone and corticosterone secretion by isolated perfused rat zona glomerulosa cells.

The effect of PGE2 and PGA1 on aldosterone and corticosterone biosynthesis by isolated perfused rat zona glomerulosa cells has been studied. Incremental doses of each of the prostaglandins tested produced a progressive rise in aldosterone (3-4 fold increase for PGE2 and 2-3 fold increase for PGA1) and corticosterone (4-8 fold for PGE2 and 2-4 fold for PGA1). The cyclo-oxygenase inhibitors indomethacin and meclofenamate however produced no effect on basal steroidogenesis. PGE2 produced a marked potentiation of angiotensin II-induced aldosterone secretion (45.7 +/- 13.6 to 144.3 +/- 19.4 pg/ml with angiotensin II alone and 78.4 +/- 16.6 to 269.9 +/- 39.5 pg/ml with angiotensin II + PGE2). In contrast, there was no effect of PGE2 on ACTH or serotonin-induced aldosterone secretion. These data show that PGE2 and PGA1 can directly stimulate rat adrenal steroidogenesis and suggest that PGE2 may play a role in mediating angiotensin II-induced aldosterone secretion by rat zone glomerulosa cells.

Adrenal Cortex↗
PubMed1985

The development and application of a direct radioimmunoassay for prostaglandin E2 utilising a gamma-labelled ligand.

A direct radioimmunoassay for urinary PGE2 has been developed, using a Pasteur Institute antibody and a gamma-labelled ligand. The assay does not require preliminary solvent extraction of the sample or any chromatographic steps. Gamma-labelled PGE2 of high specific activity was prepared by direct iodination of a PGE2-histamine derivative. Results obtained by the direct assay after serial dilution of urine samples were parallel to the standard curve. Accuracy of the method was determined by the recovery of added amounts of PGE2 to diluted urine (r = 0.094, y = 1.039x-0.535, n = 20). The lowest concentration of PGE2 distinguishable from zero was 0.063 pg/ml. The assay curve covered the range of 0.063-500 pg/ml. The assay was desensitized by increasing the concentration of both label and antiserum to obtain a curve covering the range of 2-1250 pg/ml. Intra-assay and interassay coefficient of variation were 8.6% and 12.5% respectively. Values obtained by the direct method were lower than those obtained by gas chromatography mass spectrometry (r = 0.43, y = 1.57x-3.52, n = 12) and by radioimmunoassay using 3H-PGE2 (r = 0.76, y = 0.93x+2.87, n = 12). Antibodies to PGE2 were produced in rabbits immunised with a conjugate of PGE2 covalently linked to thyroglobulin by carbodiimide reaction. The method was used to study the effect of urine flow and sodium intake on PGE2 excretion levels in normal volunteers. PGE2 excretion was flow dependent but did not vary with sodium excretion.

Antibody Specificity↗
PubMed1980

Improvement of antisera for cortisol immunoassay by reduction of endogenous hormone concentrations.

Markedly elevated concentrations of endogenous steroids in antisera may reduce the potential sensitivity of immunoassays. Attempts to raise antisera containing reduced amounts of cortisol by adrenalectomy, or concomitant administration of synthetic corticosteroid during immunisation, have met with indifferent success. Removal of cortisol, using dextran-coated charcoal in buffer of optimum molarity, may increase the average affinity constant of the antiserum, and improve the assay sensitivity and specificity.

Animals↗
PubMed1980

A simple direct solid-phase enzymeimmunoassay for cortisol in plasma.

A simple, direct solid-phase enzyme-labelled immunoassay for plasma cortisol was established using horseradish peroxidase/cortisol 21-hemisuccinate conjugate as "enzyme label. The antiserum, raised against a cortisol 21-hemisuccinate/bovine serum albumin conjugate, was coupled to cellulose to facilitate separation of free and bound steroid. Solvent extraction was avoided by the use of heat denaturation of the cortisol-binding globulin. This assay had a lower limit of sensitivity of 16.6 nmol/l and satisfied the standard criteria of accuracy and precision. Cortisol concentrations determined by enzymeimmunoassay were in excellent agreement with a gas liquid chromatography/mass spectrometry procedure (r=0.98, n=19) and also with the radioimmunoassay in current use (r=0.95, n=20). Cortisol levels after ACTH stimulatin and dexamethasone suppression in various subjects are presented. This enzymeimmunoassay is particularly applicable to the routine determination of plasma cortisol in small clinical laboratories or in those with a fluctuating workload.

Adrenocorticotropic Hormone↗