Bovine Seminal Vesicle Microsomes Research Articles

Inhibition of prostaglandin synthesis by lysolecithin

Exogenous lysolecithin inhibits prostaglandin E 2 synthesis from arachidonic acid in bovine seminal vesicle microsomes at plausible physiological levels (lysolecithin-to-protein ratios ⩾ 0.03 [w/w]) by inhibiting fatty acid cyclo-oxygenase activity. Structurally defined lysolecithins with varying fatty acid chain length exhibit varying effectiveness as inhibitors. Addition of equimolar quantities of free fatty acid lowers the lysolecithin concetration required for inhibition. Exogenous lysolecithin inhibits unstimulated and thrombin-stimulated prostaglandin E 2 synthesis from endogenous substrate in SVBalb/3T3 cells. Serum treatment of SVBalb/3T3 cells, which generates endogenous lysolecithin and free fatty acids, decreases the efficiency of conversion of free arachidonic acid to prostaglandins. These results suggest a possible role for the products of phospholipase A2 action in the regulation of prostaglandin synthesis.

Studies on the in vitro inhibition of prostaglandin synthetase by fenclorac (α, m-dichloro- p-cyclohexylphenylacetic acid) and indomethacin

Analysis of the effect of a new nonsteroidal anti-inflammatory compound, fenclorac ( αm-di-chloro- p-cyclohexylphenylacetic acid), on prostaglandin biosynthesis in vitro has shown the drug to be a potent inhibitor of this enzyme system. Fenclorac was ten times as active as indomethacin in inhibiting prostaglandin synthesis in bovine seminal vesicle microsomes. Inhibition by fenclorac was not appreciably dependent upon preincubation of drug with enzyme for maximal activity, and was reversible by dilution. The inhibitory activity of indomethacin was time-dependent and not readily reversible. Kinetic analysis indicated that fenclorac is a competitive inhibitor of prostaglandin synthe- tase, irrespective of preincubation conditions, whereas indomethacin inhibits noncompetitively if pre- incubated with enzyme, and competitively in the absence of any preincubation. Both drugs protected or stabilized prostaglandin synthetase activity under extended preincubation conditions.

Mechanism of action of novel anti-inflammatory drugs diflumidone and R-805

Two novel nonsteroidal anti-inflammatory drugs (NSAID), R-805 (4-nitro-2-phenoxymethane sulfonanilide) and R-807 (3-benzoyldinuoromethane sultonanilide, diflumidonel, inhibit the biosynthesis of prostaglandin by bovine seminal vesicle microsomes and arachidonic acid-induced aggregation of human platelets in a concentration-dependent manner. Comparison of these sulfonanilides with NSAID indicates the following order of potency: (1) vs prostaglandin synthetase: indomethacin > flufenamic acid > R-807 > R-805 > phenylbutazone ⪢ aspirin and (2) vs platelet aggregation: indomethacin > R-807 > R-805 > flufenamic acid > phenylbutazone ⪢ aspirin. Time-dependent, irreversible inhibition of prostaglandin synthetase can be demonstrated for both R-805 and R-807. These compounds also inhibit equally the formation of PGE 2 and PGF 2α, which suggests blockade of endoperoxide formation. This is the first report of inhibition of prostaglandin synthetase and platelet aggregation by drugs of this class.

Inhibition of prostaglandin biosynthesis by SL-573

The inhibition of prostaglandin biosynthesis by SL-573 (1-cyclopropylmethyl-4-phenyl-6-methoxy -2-(1H)-quinazolinone), indomethacin. and aspirin was determined by the selective extraction method of prostaglandins. using bovine seminal vesicle microsomes as enzyme sources and arachidonic acid-1-[ 14C] as a substrate. SL-573 was found to inhibit the prostaglandin biosynthesis. The relative inhibitory potencies of indomethacin. SL-573. and aspirin were 1000. 227, and 1.0, respectively. SL-573. however, differed from other drugs in the nature of the inhibition. The inhibition of SL-573 was reversible, while that of indomethacin and aspirin was irreversible and progressed time-dependently. Furthermore. SL-573 was found to prevent the progressive increase of the irreversible inhibition of indomethacin and aspirin. On the basis of such findings, the lack of the gastrointestinal side-effect of SL-573 was discussed.

Inhibition of prostaglandin biosynthesis by 2-aryl-1,3-indandiones

The effect of several 2-aryl-1,3-indandiones on the biosynthesis of prostaglandin E 2 from arachidonic acid by bovine seminal vesicle microsomes was examined. 2-Phenyl-1,3-indandione appeared to be a weak inhibitor but by introducing electron-withdrawing substituents into the phenyl ring and augmenting lipophilicity, very active compounds were obtained. Activity, however, disappeared entirely on substitution in the ortho position. Inhibition was not related to the presence of an acidic group and was irreversible in some cases. The inhibition of prostaglandin biosynthesis by 2-aryl-1,3-indandiones showed no clear relationship with anti-inflammatory action.

Flurbiprofen-Sepharose chromatography of the prostaglandin synthetase from bovine seminal vesicles

Flurbiprofen-Sepharose and Acetyl-Sepharose have been prepared by coupling dl-2-(2-fluoro-4-biphenylyl)propionic acid [Flurbiprofen] and acetic acid, respectively, to 3-(N-[3-aminopropyl])aminopropyl Sepharose 4B using a water soluble carbodiimide. The arachidonic acid oxygenase activity of solubilized bovine seminal vesicle microsomes is retarded during chromatography on Flurbiprofen-Sepharose but not Acetyl-Sepharose. Thus binding of the oxygenase to Flurbiprofen-Sepharose results from interaction with the immobilized inhibitor. However, the impure oxygenase is either not bound and/or not eluted in a biospecific manner since the abilities of flufenamic acid, R(+) and S(-)-5-cyclohexylindan-1-carnboxylic acid, and R and S-Naproxen to remove the enzyme from Flurbiprofen-Sepharose do not parallel the relative efficacies of these compounds as prostaglandin synthesis inhibitors. Nevertheless, gradient elution of arachidonic acid oxygenase activity from Flurbiprofen-Sepharose with flufenamic acid provides a 15 fold enrichment of the enzyme from solubilized bovine seminal vesicle microsomes in 80% yield indicating that this chromatographic reagent can be a powerful tool for use in purification of the prostaglandin synthetase.

The effect of pH on the production of prostaglandins E 2 and F 2α, and a possible pH dependent inhibitor

Abstract o 1. Prostaglandins E 2 and F 2α were produced in vitro by fresh rabbit renal medulla cell free homogenates, and by a rabbit renal medulla microsome preparation. The homogenate produced peaks of PGE 2 and PGE 2α production at pH 7 and 9. The microsome preparation gave a single peak at pH 7.5. Bovine seminal vesicle microsomes gave a single peak of activity at pH 8.5. 2. The supernatant from a rabbit renal medulla microsome preparation when added back to a rabbit renal medulla microsome preparation at pH 8, inhibited prostaglandin production in a dose related fashion.

Prostaglandins and cannabis—II inhibition of biosynthesis by the naturally occurring cannabinoids

A series of the naturally occurring cannabinoids were tested for possible effects on the biosynthesis of prostaglandins. Most of the substances examined were able to inhibit in varying degrees the conversion of 8,11,14-eicosatrienoic acid to prostaglandin E 1 (PGE 1) when incubated with bovine seminal vesicle microsomes. The order of activity starting with the most potent was cannabinol, cannabidiolic acid, A6tetrahydrocannabinol (Δ 6-THC), cannabidiol, cannabichromene and Δ 1-THC; cannabicyclol showed almost no inhibitory activity. It is suggested that certain of the pharmacological actions of some of these cannabinoids may be explained by a similar effect in vivo. Olivetol, which represents a partial structure for all of the compounds tested, showed high activity, indicating that the inhibitory power of the cannabinoids resides in the aromatic portion of the molecule.

Relationship between inhibition of prostaglandin synthesis and drug efficacy: Support for the current theory on mode of action of aspirin-like drugs

Summary The synthesis of Prostaglandin E2 (PGE2) from 5,8,11,14-eicosatetraenoic acid (arachidonic acid) by bovine seminal vesicle microsomes can be inhibited by the non-steroidal anti-inflammatory agents indomethacin, naproxen, its enantiomer and aspirin. The relative inhibitory potencies are 2140 to 150 to 2 to 1. These values correlate in general with anti-inflammatory, anti-pyretic and analgesic activities of these compounds, as evaluated in a number of animal models. Since the prostaglandins have been implicated in inflammation, pyresis and pain, this positive correlation adds support to the hypothesis that amode of action of aspirin-like drugs is to inhibit the biosynthesis of prostaglandins.