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Biomedical subjects

A Hassid

Publications and source records attributed to A Hassid.

At least 55 records · Page 3Linked to original sources
PubMed1983

Vasoconstrictor-evoked prostaglandin synthesis in cultured vascular smooth muscle.

We investigated the hypothesis that vasopressin, angiotensin II, and norepinephrine stimulate the synthesis of vasodilatory prostaglandins in cultured vascular smooth muscle cells from rat mesenteric arteries. The major prostaglandin synthesized by subcultured vascular smooth muscle cells was PGI2 (measured as its stable metabolite 6-keto-PGF1 alpha) followed by 1/20th to 1/40th as much PGF2 alpha and PGE2. Vasopressin and angiotensin II dose dependently increased prostaglandin synthesis with a half-maximal stimulatory concentration of the order of 1 X 10(-8) M for both peptides. However, vasopressin could provoke the synthesis of two to three times as much PGI2 as angiotensin II, at maximally effective concentrations. Vasopressin's ability to provoke prostaglandin synthesis depended on its pressor activity as demonstrated by the ability of a potent antipressor analogue of vasopressin, [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid), 2-(O-methyl)tyrosine] arginine vasopressin, to completely inhibit vasopressin-provoked prostaglandin synthesis. Moreover, 1-desamino-8-D-arginine vasopressin, an analogue having full antidiuretic but no pressor activity was much less effective than vasopressin as a prostaglandin-stimulatory agent. Unlike peptide vasoconstrictors, norepinephrine (10(-9) to 10(-5) M) had no ability to stimulate prostaglandin synthesis in vascular smooth muscle cells. We conclude that the potent vasodilator PGI2, released from vascular smooth muscle cells, may buffer the peptide-induced vasoconstriction.

Angiotensin II↗
PubMed1982

Lipoxygenase activity in rat kidney glomeruli, glomerular epithelial cells, and cortical tubules.

We examined the possibility that renal glomerular and cortical tubular tissue has lipoxygenase activity in addition to the well established cyclo-oxygenase pathway of arachidonic acid metabolism. Homogenized rat kidney glomeruli, in the presence of meclofenamate (33 microM) and divalent cation ionophore A23187 (3 microM), metabolized octatritiated arachidonic acid to 12-hydroxyeicosatetraenoic acid and lesser amounts of 80 and/or 9-hydroxyeicosatetraenoic acid. These products were identified by thin layer chromatography, high performance liquid chromatography, and gas chromatography-mass spectroscopy. In order to rule out the synthesis of hydroxylated fatty acids by platelets and leukocytes entrapped in the glomeruli, we studied lipoxygenase products in glomerular epithelial cells after 9 days in cell culture. Homogenized glomerular epithelial cells converted octatritiated arachidonic acid to 12-hydroxyeicosatetraenoic acid solely. The lipoxygenase activity in cortical tubules was substantially less than in glomeruli and only 12-hydroxyeicosatetraenoic acid was synthesized. The production of hydroxyeicosatetraenoic acid by lipoxygenase inhibitors, nordihydroguaiaretic acid, 5,-homogenized glomeruli, glomerular epithelial cells, and cortical tubules was inhibited by three 8,11,14-eicosatetraynoic acid, and 1-phenyl-3-pyrazolidone. These data demonstrate that there is lipoxygenase activity in rat kidney glomeruli, glomerular epithelial cells and to a lesser extent cortical tubules, and may imply a role of the lipoxygenase products in the regulation of normal glomerular function and inflammatory disease of the kidney.

Animals↗
PubMed1982

Prostacyclin substitution for heparin in long-term hemodialysis.

We studied prostacyclin as a substitute for heparin in 12 patients who underwent maintenance hemodialysis. All subjects underwent initial hemodialysis with prostacyclin as the sole anticoagulant; 10 of the 12 were restudied during heparin hemodialysis. Few adverse reactions occurred during prostacyclin hemodialysis in the 10 patients in whom dialysis was performed against a bicarbonate-containing dialysate; however, significant hypotension developed in two subjects when an acetate bath was used. Platelet aggregation progressively decreased during prostacyclin hemodialysis (p less than 0.02), but not during heparin hemodialysis, and returned toward control values after hemodialysis. Platelet thromboxane release decreased during both prostacyclin and heparin hemodialysis. Intradialytic percent decrements in serum urea nitrogen and creatinine were greater during prostacyclin than heparin administration (42 +/- 2.9 percent versus 36 +/- 2.6 percent [p less than 0.05] and 33 +/- 2.6 percent versus 29 +/- 2.1 percent [0.05 less than p less than 0.1], respectively). The plasma concentrations of 6-keto-prostaglandin-F1 alpha, a prostacyclin metabolite, reached peak levels by 120 minutes of hemodialysis and declined biexponentially toward predialysis concentrations during 120 minutes after hemodialysis, thereby providing an index of cumulative prostacyclin dosage. We conclude that prostacyclin is not only a safe alternative to heparin anticoagulation during hemodialysis, but that prostacyclin might also increase the efficiency of hemodialysis.

6-Ketoprostaglandin F1 alpha↗
PubMed1981

Prostaglandin biosynthesis by lapine articular chondrocytes in culture.

Secondary monolayer and spinner cultures of rabbit articular chondrocytes released into the culture medium prostaglandins the synthesis of which was inhibited by sodium meclofenamate. The prostaglandins measured by radioimmunoassay were, in order of decreasing abundance, prostaglandin E2, 6-oxo-prostaglandin F1 alpha (the stable metabolite of prostacyclin) and prostaglandin F2 alpha. Several lines of evidence indicated that chondrocytes synthesize little if any thromboxane B2 (the stable metabolite of thromboxane A2). The presence of prostaglandins was confirmed by radiometric thin-layer chromatography of extracts of culture media incubated with [3H]arachidonic acid-labeled cells. In monolayer culture, chondrocytes synthesized immunoreactive prostaglandins in serum-free as well as serum-containing medium. Monolayer chondrocytes produced higher levels of prostaglandin E2 relative to 6-oxo-prostaglandin F1 alpha than did spinner cells, but the latter synthesized more total prostaglandins. The identity of endogenous prostaglandins as well as those synthesized in short-term culture by rabbit cartilage slices was compared to those produced by chondrocytes in long-term culture. Chondrocytes synthesized all of the prostaglandins found in articular cartilage. Minimal quantities of thromboxane B2 were detected in cartilage. A higher percentage of 6-oxo-prostaglandin F1 alpha relative to other prostaglandins was found in cartilage than in either monolayer or spinner chondrocyte cultures. These results demonstrate that articular chondrocytes synthesize prostaglandins and prostacyclin. These prostaglandins may exert significant physiological effects on cartilage, since exogenous prostaglandins depress chondrocyte sulfated-proteoglycan synthesis and may even promote proteoglycan degradation.

6-Ketoprostaglandin F1 alpha↗
PubMed1980

Thromboxane A2 mediates augmented polymorphonuclear leukocyte adhesiveness.

We examined the role of prostaglandins and thromboxanes as mediators of plasma-dependent increased polymorphonuclear leukocyte adhesiveness induced by Escherichia coli lipopolysaccharide. The cyclo-oxygenase inhibitors-indomethacin and d,l-6-chloro-alpha-methyl-carbozole-2-acetic acid (R020-5720)-reduced lipopolysaccharide-induced adherence of polymorphonuclear leukocytes by 74 and 62%, respectively. In addition, inhibitors of thromboxane synthetase-imidazole, 9,11-azoprosta-5,13-dienoic acid, and 1-benzylimidazole-suppressed the stimulation of adherence by 31, 66, and 83%, respectively. Exogenous prostaglandins E(1), E(2), and F(2)alpha did not increase polymorphonuclear leukocyte adherence, nor were they detected in significant quantities in supernates of polymorphonuclear leukocytes exposed to lipopolysaccharide. However, inhibitors of both cyclo-oxygenase and thromboxane synthetase reduced increases in adherence induced by arachidonic acid (10 mug/ml), suggesting that lipopolysaccharide-mediated increases in adherence were due to an arachidonic acid product other than prostaglandin E(2) or F(2)alpha. 8,11,14-Eicosatrienoic acid, a precursor of monoenoic prostaglandins, did not enhance polymorphonuclear leukocyte adhesiveness. We next demonstrated lipopolysaccharide-stimulated generation, by polymorphonuclear leukocytes, of a labile, low molecular weight, dialyzable substance capable of enhancing the adherence of unstimulated leukocytes. In parallel experiments, a 10-fold increase in immunoreactive thromboxane B(2) over basal levels was detected after exposure of leukocytes to lipopolysaccharide. The inhibition of lipopolysaccharide enhancement of adherence by specific rabbit antibodies to thromboxane B(2) strongly supported a primary role for thromboxane A(2) as the mediator of the observed increases in adherence. Lipopolysaccharide-stimulated purified platelets did not increase leukocyte adherence, whereas thrombin-stimulated platelets did increase adherence. These studies suggest that lipopolysaccharide stimulates polymorphonuclear leukocytes to produce thromboxane A(2), which enhances their adhesiveness to nylon.

Cell Adhesion↗
PubMed1980

The effect of arginine vasopressin and its analogs on the synthesis of prostaglandin E2 by rat renal medullary interstitial cells in culture.

Arginine vasopressin (AVP) stimulates renal prostaglandin (PG) production which is thought to inhibit vasopressins' antidiuretic action. Using rat renal medullary cells in culture (RMIC), we compared the ability of the following peptides which possess different biological activities to stimulate prostaglandin biosynthesis: AVP (high antidiuretic and pressor activities); 1-desamino-8-D-arginine vasopressin (a synthetic peptide with high antidiuretic and no pressor activity); and oxytocin (intermediate pressor, low antidiuretic activity). Radiometric thin-layer chromatography of supernatant media from cells incubated with octatritiated or [14C]arachidonic acid revealed only one radiolabeled peak which co-migrated with PGE2. Radioimmunoassay confirmed that PGE2 was the only prostaglandin synthesized by RMIC. Incubation of cells with AVP (1 nM to 3 microM) increased PGE2 synthesis measured by radioimmunoassay in a concentration-dependent fashion up to 2 1/2-fold over control; 1-desamino-8-D-arginine did not increase PGE2 synthesis. Oxytocin stimulated PGE2 synthesis, but was less potent than AVP. Preincubation of RMIC with [1-(beta-mercapto-beta, beta-cyclopentamethylene propionic acid)-4-valine, 8-D-arginine]vasopressin, a synthetic nonpressor, nonantidiuretic antagonists of AVP's pressor activity, completely blocked the ability of AVP to stimulate PGE2 synthesis. We conclude that the ability of AVP to stimulate PGE2 synthesis in RMIC is related to its pressor, not its antidiuretic, activity.

Animals↗
PubMed1979

Prostaglandin synthesis in isolated rat kidney glomeruli.

Isolated rat kidney glomeruli converted octatritiated arachidonic acid to several prostaglandins whose production was inhibited by meclofenamate. These were, in order of decreasing abundance, prostaglandin F2 alpha, prostaglandin E2, 6-oxo-prostaglandin F1 alpha, thromboxane B2, and prostaglandin D2. These products were identified by thin-layer chromatography, before and after treatment with potassium hydroxide or sodium borohydride. Prostaglandins F2 alpha and E2 were also determined by radioimmunoassay. The major product made by glomeruli was an unidentified substance(s), whose appearance was partially inhibited by meclofenamate, and was likely to be a hydroxylated fatty acid(s). The specific activity of glomerular fatty acid cyclo-oxygenase (EC 1.14.99.1), based on radioimmunoassay for prostaglandins E2 and F2 alpha, was 10- to 40-fold higher than that of cortical tubular enzyme. These data demonstrate that glomeruli have the capability of synthesizing an array of end-products from arachidonic acid. These prostaglandins may exert important physiologic effects, because renin secretion and arteriolar resistance are regulated by the glomerulus and the afferent and efferent arterioles.

Animals↗
PubMed1977

Induction of fatty acid cyclooxygenase activity in canine kidney cells (MDCK) by benzo(a)pyrene.

Canine kidney cells (MDCK) in which [3H]arachidonic acid was esterified in the cellular lipids released increased levels of radioactive prostaglandins and arachidonic acid into the medium when cultured in the presence of benzo(a)pyrene. When MDCK cells were cultured in the presence of benzo(alpha)pyrene and 7,8-benzoflavone, this increased release was not observed. MDCK cells incubated with benzo(a)pyrene also converted exogenous arachidonic acid into prostaglandins more effectively than cells grown in its absence. 7,8-Benzoflavone inhibited this benzo(a)pyrene effect. Microsomes, prepared from benzo(alpha)pyrene-treated MDCK cells synthesized prostaglandin F2alpha from arachidonic acid more effectively than nontreated cells.

Arachidonic Acids↗
PubMed1977

Microtubular protein catalytic interactions with nucleotides.

Purified tubulin prepared from pig brain in the absence of added guanine nucleotides contains 1 mol each of GDP and GTP/mol of tubulin. Incubation of a tubulin preparation with inorganic [32P]phosphate results in the incorporation of 32P into tubulin-associated GDP and GTP. Typically, in a 5-h incubation, 0.45 mM 32Pi reacts with 22 muM tubulin to form 3.3 muM [32P]GDP, and 0.3 muM [32P]GTP. The yield of labeled nucleotide is decreased as the result of a hydrolase activity associated with the preparation. The [32P]GTP is exclusively beta-labeled and is therefore formed by phosphorylation of [32P]GDP by a phosphate donor other than inorganic phosphate, most likely by nonradioactive GTP. Added GDP significantly decreases the yield of labeled GTP, but increases the yield of labeled GDP in a manner that is consistent with a partial protection against [32P]GDP hydrolysis, but not consistent with significant additional [32P]GDP formation. Added GMP is an inhibitor of both labeling activities associated with the preparation, although it has no effect on the hydrolase activity. Added ADP (0.4 MM) does not form labeled ADP or ATP and does not influence the labeling of GDP or GTP. The formation of [32P]GDP was shown to occur by an exchange mechanism rather than through net synthesis from GMP and Pi. These results provide evidence for a reversible guanidylation of the protein. The labeling activity is always specifically associated with highly purified tubulin preparations. Microtubular protein preparations are found to catalyze an exchange of oxygen from H218O into inorganic phosphate. Thus, there are two distinct catalytic properties associated with tubulin.

Animals↗