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Sera to conjugates of prostaglandins El and E2 with bovine serum albumin and bovine thyroglobulin were raised in rabbits to determine their specificity for these prostaglandins. Antisera to bovine serum albumin conjugates of prostaglandins El and E, were more reactive against prostaglandins A and B respectively. In contrast, the sera prepared with conjugates of thyroglobulin with prostaglandins El and E2 displayed marked specificity for the homologous antigens and only minimal cross-reactivity with prostaglandins A and B respectively. These latter antisera were used to develop a sensitive radioimmunoassay for the E prostaglandins.Specific antisera are a necessary prerequisite for the determination of prostaglandins El and E2 in biological fluids and tissue extracts. Earlier attempts to produce such sera involved coupling prostaglandins to bovine serum albumin or keyhole limpet hemocyanin followed by immunization of rabbits with the resulting protein-prostaglandin conjugates. Jaffe et al. [l] immunized rabbits with prostaglandin El conjugates with albumin or hemocyanin but found that their sera were more specific for prostaglandin Al than for El. Similarly, Levine et al. [2] found that the activity of sera raised to prostaglandin El-albumin conjugates were primarily directed against prostaglandin B,. Comparable results were obtained by Yu and Burke [3] and also by Zusman et al. [4] whose prostaglandin E2 sera were mainly reactive against A2. As a result of these studies, several investigators [2,3] have concluded that it would be very difficult to raise sera that are highly specific for the E prostaglandins and that some other protein carrier might promise more specific products. As Skowsky and Fisher [5] have Trivial Names. Prostaglandin El, 1 Ia,l5(S)-dihydroxy-9-ketoprost-13-rrans-enoic acid ; prostaglandin El, 1 la,l5(S)-dihydroxy-9-ketoprosta-5-cis,l3-trans-dienoic acid; Prostaglandin F,,, 9r,l la, IS(S)-trihydroxyprost-13-trans-enoic acid; prostaglandin Fzo. 9a, 1 1 a. 1 5(S)-trihydroxyprosta-5-cis, 13 -trans-dienoic acid ; prostaglandin A,, 15(S)-hydroxy-9-ketoprost-lO,l3-trans-dienoic acid; prostaglandin Al, 15(S)-hydroxy-9-ketoprosta-5-cis,lO,l3-transtrienoic acid; prostaglandin B,, lS(S)-hydroxy-9-ketoprost-8(12), 13-trans-dienoic acid ; prostaglandin B2, IS(S)-hydroxy-Y-ketoprosta-5-cis,b( 12), 13-trans-trienoic acid.shown that sera to thyroglobulin-hormone complexes are more specific than those to the analogous poly-Llysine conjugates, we decided to investigate the specificity of sera prepared with conjugates of thyroglobulin with prostaglandin El or E,, and to compare the results with those obtained with the analogous albumin conjugates. While this study was in progress, two reports [6,7] appeared describing the production of prostaglandin E specific sera using bovine serum albumin as the protein carrier of the immunizing conjugate. After completion of this work, a report appeared [8] on the specificity of prostaglandin El antiserum using thyroglobulin-prostaglandin El conjugates. MATERIALS AND ME...

Cyclic prostaglandin endoperoxides prostaglandin G2 and HZ are intermediates formed in the biosynthesis of prostaglandins from arachidonic acid. These endoperoxides can be converted chemically or enzymatically to prostaglandins E2, D2 and Fza. The effects of several reducing compounds on the chemical and enzymatic transformations of prostaglandins GZ and HZ were studied in order to determine the possible existence of two alternative enzymatic pathways for the conversion of prostaglandin G2 to prostaglandins.The chemical transformation of prostaglandin H2 to prostaglandins by cleavage of the 9, 11 -cycloendoperoxide ring was unaffected by the presence of reduced glutathione, heme or tryptophan while hydroquinone and mercaptoethanol promoted the chemical reduction to prostaglandin F2.. In contrast the enzymatic transformation of prostaglandin H2 to prostaglandins by a solubilized prostaglandin synthetase from sheep vesicular gland was unaffected by hydroquinone or mercaptoethanol, but was markedly stimulated by reduced glutathione to yield mainly prostaglandin Ez.Prostaglandin G2 transformation to prostaglandins involves cleavage of the 9, 1 1 -endoperoxide ring and a reduction of the 15-hydroperoxy group. The chemical reduction in buffer of the 15-hydroperoxy group is not affected by the presence of reduced glutathione, hydroquinone, heme or tryptophan. In contrast, the enzymatic reduction of the 15-hydroperoxy group is catalyzed by the solubilized prostaglandin synthetase and is further stimulated by reduced glutathione and hydroquinone. Results are presented which indicate that the enzymatic conversion of prostaglandin G2 to prostaglandins can proceed via two alternative pathways, one involving the intermediate formation of prostaglandin H2 and the other the formation of 15-hydroperoxy prostaglandins. The latter pathway appears to be the major pathway for the enzymatic conversion of prostaglandin G2 to prostaglandins.The biosynthesis of prostaglandins from arachidonic acid by sheep or bovine seminal vesicles involves several distinct steps with formation of two endoperoxide intermediates designated prostaglandin G2 and H2 [ 1,2] or 15-hydroperoxy prostaglandin R2 and R2 respectively [3]. Several reducing agents were shown to affect the overall rate of prostaglandins formation and the relative amounts of the various prostaglandin products formed. Reduced glutathione (GSH) and hydroquinone were shown to stimulate the biosynthesis of prostaglandin E2 from arachidonic acid in Triviul Nunies. Prostaglandin Ez, 1 lx,l 5(S)-dihydroxy-9-ketoprosta-5-cis,l3-trans-dienoic acid; prostaglandin F z~, 9n,1 ln,l5(S)-trihydroxyprosta-S-ris,l3-tram-dienoic acid; prostaglandin Dz, 9n,-1 S(S)-dihydroxy-lI -ketoprosta-5-cis-1 3-trans-dienoic acid ; prostaglandin Gz, 9n,l Ix-epidioxy-15(S)-hydroperoxy-S-ci~,l3-tr~n~~-prostadienoic acid; prostaglandin Hz, 9n,l lr-epidioxy-lS(S)-hydroxy-5-cis, 13-trans-prostadienoic acid. sheep vesicular gland microsomes [4] and in bovine seminal vesicle microsomes [5-71. Heme was also reported ...

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