Sheep Seminal Vesicles Research Articles

Inhibition of prostaglandin synthetase by anti-tumour agents

The effect of a number of anti-tumour agents on prostaglandin (PG) production from arachidonate by sheep seminal vesicles has been investigated. Of the drugs examined only those belonging to the alkylating agent type series showed inhibition of enzyme activity. Unlike most inhibitors of PG synthetase (EC 1.14.99.1) these agents caused an inhibition of prostaglandin E 2 (PGE 2) production, while unaffecting the formation of prostaglandin F 2α (PGF 2α). This suggests the site of inhibition is the isomerase converting prostaglandin H 2 (PGH 2) to PGE 2. Kinetic studies indicated that merophan [DL- o-(di-2-chloroethylamino)phenylalanine] inhibited the synthetase competitively with respect to substrate. The kinetics of the inhibition were also consistent with the formation of a reversible enzyme-alkylating agent complex prior to irreversible inactivation of the enzyme. The inactivation process could be described by the Main equation from which a dissociation constant (Kd) and a reaction rate constant (k 2) were calculated. The inhibition of PG synthetase may be important in the anti-tumour effect of these agents.

Stimulation of prostaglandin biosynthesis by lipoic acid

Enzyme preparations from sheep seminal vesicles display an enhanced ability to synthesize prostaglandins, particularly prostaglandin F from polyunsaturated fatty acids if α-lipoic acid is present in the incubation mixture prior to the addition of fatty acid. The stimulation by lipoate is reversible, time dependent, and involves modifications of V and K m for oxygenase activity. Product studies, structure vs. activity studiesand purification data indicate that lipoate exerts its effect by a mechanism distinct from a glutathione-like metabolism of the endoperoxide linkage in prostaglandin G and prostaglandin H. In addition, product studies suggest that lipoate is not a cofactor for the endoperoxide isomerase component of prostaglandin synthetase. Purification of the endoperoxide synthesizing activity by ion-exchange chromatography and isoelectric focusing yields preparations which are more responsive to lipoate than microsomal preparations.

Comparative effects of aspirin and diflunisal on prostaglandin synthetase from human platelets and sheep seminal vesicles.

1. We have compared the effects of diflunisal on prostaglandin (PG) synthetase from human platelets and sheep seminal vesicles (SSV) by measuring malonaldehyde, PG products, and rabbit aorta contraction. 2. Aspirin inhibits PG synthetase by covalently acetylating the enzyme. Inhibition is dependent on time and aspirin concentration. Aspirin is 37‐fold more potent in inhibiting enzyme in human platelets compared with enzyme from SSV. 3. Diflunisal inhibits PG synthetase from intact human platelets and SSV equally (50% inhibition at 3‐5 micronM). The drug does not covalently modify the enzyme, and inhibition is not time dependent. Diflunisal probably acts at a site similar to aspirin since the drug will inhibit acetylation of the enzyme by aspirin. 4. The results suggest that diflunisal is relatively less inhibitory to platelet function than is aspirin.

Catabolism of an isolated, purified intermediate of prostaglandin biosynthesis by regions of the adult rat kidney

1. 1. A heat labile, cold-stable, stannous chloride-reducible intermediate of prostaglandin biosynthesis was formed in good yield (>60%) from 3H-labeled arachidonic acid during brief incubations (30–90 s, 37° C) with sheep seminal vesicle microsomes in the presence of p-hydroxymercuribenzoate (4 mM). This intermediate appears to have properties similar to one of the endoperoxides (15-hydroxyprostaglandin-9,11-endoperoxide) recently isolated by Hamberg and Samuelsson (Proc. Natl. Acad. Sci. U.S. (1973) 70, 889–903) and Nugteren and Hazelhof (Biochim. Biophys. Acta. (1973) 326, 448–461). 2. 2. Treatment of the purified intermediate with homogenates of rat kidney cortex, medulla and papilla resulted within 2 min (37° C) in complete conversion into several compounds including prostaglandins E 2 and F 2 α . The main product (40–50% yield) formed by papilla homogenates was prostaglandin E 2. The conversion into prostaglandin E 2 was largely abolished by previous boiling of the homogenate whereas the conversion into prostaglandin F 2α was not. The intermediate was stable in buffer for the same period of incubation. 3. 3. The ratio of tritiated prostaglandins E 2 : F 2α obtained were: papilla, 1.90; medulla 0.76; cortex 0.48. 4. 4. These observations indicate that both types of prostaglandins can be formed by all three regions of the rat kidney and that regional differences exist in the proportion of E 2 : F 2α a that is formed. Whereas prostaglandin E 2 is mostly formed by an enzymatic process, prostaglandin F 2α is not.

Inhibition of prostaglandin synthase by pirprofen: Studies with sheep seminal vesicle enzyme

1. 1. Pirprofen, racemic 2-[3-chloro-4(3-pyrrolinyl)phenyl] propionic acid, was evaluated for its ability to inhibit the conversion of arachidonic acid into prostaglandin E 2 by sheep seminal vesicle prostaglandin synthase in vitro. 2. 2. The compound proved to be a potent inhibitor with a K i value of about 1.2 μM. Like indomethacin, aspirin and certain other non-steroidal anti-inflammatory drugs, pirprofen inhibited the enzyme competitively with respect to substrate. Unlike most non-steroidal anti-inflammatory drugs, however, pirprofen did not promote time-dependent inactivation of the enzyme. It behaved as a competitive, reversible inhibitor, whereas most of the other agents acted as competitive, irreversible inhibitors. 3. 3. The results suggest that inhibition of prostaglandin synthesis accounts in large part for the pharmacological effects of pirprofen.

Diclofenac sodium (GP 45840, voltaren), a potent inhibitor of prostaglandin synthetase

Diclofenac sodium, the sodium salt of o-(2,6-dichlorophenylamino)-phenylacetic acid (GP 45840, Voltaren), is a potent inhibitor of sheep seminal vesicle prostaglandin synthetase in vitro. Like indomethacin, aspirin and certain other nonsteroidal anti-inflammatory drugs, it acts as a competitive and irreversible inhibitor. It is suggested that diclofenac sodium exerts most of its pharmacological effects via inhibition of prostaglandin synthetase.

Effects of local anaesthetics on prostaglandin biosynthesis in vitro

1. 1. The spontaneous formation of prostaglandins in homogenates of bovine seminal vesicles was stimulated by Ca 2+ and inhibited by EDTA. The effects of various local anaesthetics were studied over a concentration range of 0.01–20 mM. The local anaesthetics used inhibited prostaglandin formation, except cocaine, lidocaine and mepivacaine. The order of potency was benzocaine > chlorpromazine > dibucaine > tetracaine > procaine > butacaine. 2. 2. Phospholipase A 2 activity in homogenates of bovine seminal vesicles, estimated with sonicated radioactive phosphatidylethanolamine as substrate, was stimulated by Ca 2+ and inhibited by EDTA. At a concentration of 1 mM benzocaine, lidocaine and mepivacaine had no significant effect. The other local anaesthetics inhibited in the order chlorpromazine > dibucaine > tetracaine > butacaine > cocaine > procaine. 3. 3. In acetone-pentane powder preparations of sheep seminal vesicles the prostaglandin synthetase activity was studied by adding arachidonic acid as substrate. Ca 2+ inhibited and EDTA stimulated the prostaglandin synthetase activity. At 1 mM final concentrations only chlorpromazine > benzocaine > dibucaine > butacaine inhibited the conversion to prostaglandin, whereas procaine, tetracaine, cocaine, lidocaine and mepivacaine had no effect or even stimulated the conversion. 4. 4. Thus chlorpromazine, dibucaine and butacaine inhibit prostaglandin biosynthesis in a non-specific manner, whereas benzocaine acts only on the prostaglandin synthetase. Tetracaine and possibly procaine specifically inhibit prostaglandin biosynthesis by interference with phospholipase A 2 activity. 5. 5. The present work does not imply that local anaesthesia is mediated by inhibition of prostaglandin biosynthesis. This inhibition may be a side effect of local anaesthetics.

Indomethacin and aspirin inhibition of prostaglandin E 2 synthesis by sheep seminal vesicles microsome powder

Sheep seminal vesicles microsome powder was used as a source of prostaglandin synthetase in studies on the nature of inhibition of prostaglandin synthesis by indomethacin and aspirin. Irdomethacin inhibition was found to be highly irreversible, although partial recovery of synthetase activity was obtained after extensive dialysis. A major difference was observed between the effects of aspirin and indomethacin on prostaglandin synthetase activity in seminal vesicles slices. Enzyme activity in microsomes prepared from slices incubated with aspirin was markedly inhibited while the activity in microsomes prepared after incubation with indomethacin was not affected. These results suggest that indomethacin may penetrate intracellularly very slowly, or not at all, and raise a question as to whether the inhibition by indomethacin in vivo is mediated via direct inhibition of prostaglandin synthesis.

Structural requirements of acetylenic fatty acids for inhibition of soybean lipoxygenase and prostaglandin synthetase

The conversion of linoleic acid to its hydroperoxide by soybean lipoxygenase and the conversion of arachidonic acid to prostaglandin E 2 by a preparation of sheep seminal vesicles, both previously shown to be irreversibly inhibited by eicosa-5,8,11, 14-tetraynoic acid, are similarly inhibited by octadeca-9,12-diynoic acid. No other member of a series of ten diynoic fatty acids, nor any of fifteen positional isomers of octadecynoic acid, showed detectable inhibition. Of a group of four isomeric octadecenynoic acids, having one acetylenic and either a cis- or trans-ethylenic bond in the 9 or 12 positions, none significantly inhibited soybean lipoxygenase, whereas only one, octadec-cis-9-en-12-ynoic acid failed to strongly inhibit prostaglandin synthesis.

Polyhydroxy cyclic ethers formed from tritiated arachidonic acid by acetone powders of sheep seminal vesicles.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPolyhydroxy cyclic ethers formed from tritiated arachidonic acid by acetone powders of sheep seminal vesiclesC. Pace-AsciakCite this: Biochemistry 1971, 10, 20, 3664–3669Publication Date (Print):September 1, 1971Publication History Published online1 May 2002Published inissue 1 September 1971https://doi.org/10.1021/bi00796a005RIGHTS & PERMISSIONSArticle Views42Altmetric-Citations40LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (679 KB) Get e-Alerts Get e-Alerts

Properties of a novel preparation of prostaglandin synthetase from sheep seminal vesicles

1. (1) The objective of this investigation was to improve yields of prostaglandin Es using the prostaglandin synthetase system derived from sheep seminal vesicular glands so that a broad program of biological evaluation of prostaglandin E 2 and derivatives could be undertaken and supported. 2. (2) The synthetase associated with the microsomes can be precipitated by either acidification to pH 4.8–5.0, or alternatively by adding acetone to a concentration of 30%, and then recovered by centrifugation at 3000–4000 × g. An acetone-pentane powder prepared from this microsomal precipitate retains full prostaglandin synthetase activity. 3. (3) The conversion of arachidonic acid to prostaglandin E 2 by this acetonepentane powder preparation proceeds rapidly and approaches an asymptote within 10 min at 30°. At this point, the enzyme may be readily removed from the incubation mixture by centrifugation and added to fresh medium. The reaction begins again and continues to nearly the same extent as the initial incubation. This, and other evidence discussed, suggests that the prostaglandin synthetase system is inhibited by one or more products of the reaction. Cycling the enzyme 10 times with judicious additions of fresh enzyme to compensate for losses results in yields 3-fold higher than were hitherto possible using whole tissue homogenates. 4. (4) Some other important properties of this enzyme preparation are discussed.

Inhibition of prostaglandin biosynthesis by eicosa-5,8,11,14-tetraynoic acid

Conversion of arachidonic acid to prostaglandin E 2 by acetone powders of sheep seminal vesicles was irreversibly inhibited by low concentrations of eicosa-5,8,11,14-tetraynoic acid. This compound also inhibited the hydroxylation of linoleic and linolenic acids by the tissue preparation, thereby preventing the elimination of the inhibitory effects of these polyethylenic acids. The tetraacetylenic acid can therefore limit prostaglandin biosynthesis both by its direct effect on prostaglandin synthetase and by preventing the inactivation of endogenous inhibitors.

Enzyme inhibition by acetylenic compounds

Soybean lipoxidase and prostaglandin synthetase from sheep seminal vesicles are subject to powerful inhibition by 5,8,11,14-eicosatetraynoic acid, apparently by a slow but irreversible attack on the enzymes. It is postulated that inhibition may result from conversion of the acetylenic compound to a reactive allene by the enzymes studied, as has been proposed in the inhibition of β-hydroxydecanoyl thioester dehydrase by 3-decynoyl-N-acetylcysteamine.

Polyhydroxylated by-products of the enzymatic conversion of tritiated arachidonic acid into prostaglandins by sheep seminal vesicles

In the biosynthesis of prostaglandins by sheep seminal vesicles, the prostaglandin E fraction after treatment with alkali to convert PGE2 into PGB2 contained four major compounds still migrating on t.l.c. in the PGE region: (I), (II), and (IV) were derived from triatiated arachidonic acid and (III) was derived from endogenous eicosatrienoic acid.

Hypertension, natriuresis, and the renal prostaglandins.

Editorials1 May 1969Hypertension, Natriuresis, and the Renal ProstaglandinsJAMES B. LEE, M.D.JAMES B. LEE, M.D.Search for more papers by this authorAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/0003-4819-70-5-1033 SectionsAboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail ExcerptProstaglandins are a group of cyclical fatty acids with diverse potent biological activities which were discovered independently in the early 1930's by Goldblatt (1) and von Euler (2). In 1962 Bergström, Ryhage, Samuelsson, and Sjövall (3) elucidated the chemical structure of two distinct classes of prostaglandins, prostaglandins E and prostaglandins F (PGE and PGF). The PGE compounds lower blood pressure and stimulate nonvascular smooth muscle to contract; the PGF compounds are without vasodepressor effects but, like PGE, possess intestinal-smooth-muscle-stimulating activity. The widespread occurrence of these compounds is evidenced by their isolation from such sources as sheep seminal vesicles; sheep, pig,...

The origin of oxygen incorporated during the biosynthesis of prostaglandin E 1

A clinical experiment wherein prostaglandin E1 was formed using sheep seminal vesicle homogenates is explained. The prostaglandin E1 which was produced was analyzed by mass spectrometry and gas chromatography. The results showed that of the 3 oxygen atoms incorporated during the procedure 2 appear as hydroxyl groups and 1 as a keto group. The study shows that the oxygens of the 2 hydroxyl groups used in the biosynthesis of prostaglandin E1 derive from oxygen gas. No conclusions can be drawn regarding the origin of the keto oxygen.

The formation of fructose in the ocular lens.

Free fructose in normal mammalian tissue has been shown to occur only in certain accessory sexual tissues of rodents,1in sheep seminal vesicles,2and placenta of ungulates.3As a result of secretion by the seminal vesicle fructose is a normal constituent of semen in many animals.4,5Fructose also occurs in the fetal blood of ungulates,6arising by a process involving sorbitol as an intermediate.7Its occurrence in lenses of rats8and rabbits8,9appears to be an exception to the generalization that free fructose is normally found only in tissues associated

Le mécanisme de la formation du fructose séminal et du fructose foetal

1. 1. Slices of sheep seminal vesicles irreversibly convert glucose to sorbitol and sorbitol to fructose. The fructose formed from [1- 14C] glucose is labelled only in position 1. 2. 2. The same conversions are catalysed by extracts of seminal vesicles in the presence of glucose-6-phosphate, TPN and DPN. 3. 3. The conversion of glucose to fructose and sorbitol by slices or extracts is inhibited by glucosone and glucuronolactone. The conversion of sorbitol to fructose is inhibited by ethylenediaminetetraacetate, which inactivates the ketose reductase. 4. 4. These observations as well as the presence of sorbitol in the fresh gland indicate that the conversion of glucose to fructose by seminal vesicles takes place according to the reactions: ▪ 5. 5. The presence of the aldose reductase in the placenta of the ewe, of the ketose reductase in the liver of the foetus and of sorbitol in the foetal blood indicates that the foetal fructose can be formed by the same mechanism, glucose being converted to sorbitol in the placenta and sorbitol to fructose in the liver. 6. 6. The various mechanisms by which glucose could be converted to fructose are discussed.