Organ selective conversion of prostaglandin D2 to 9 alpha, 11 beta-prostaglandin F2 and its subsequent metabolism in rat, rabbit and guinea pig.
Cell-free 100,000 g supernatants from liver, kidney, lung and caecum of rat, rabbit and guinea-pig were compared for their ability to transform prostaglandins F2 alpha, D2, E2 and 9 alpha, 11 beta-prostaglandin F2 (11epi-PGF 2 alpha) to metabolic products. Experiments utilized multitritiated substrate PGs, with assessment of biotransformation by TLC, HPLC and GC/MS. PGF2 alpha was converted via the sulphasalazine analogue-inhibitable NAD+-dependent 15-hydroxy-prostaglandin dehydrogenase pathway (15-PGDH), with high activity (greater than 5 pmol/min/mg protein) in all 12 systems except rat and rabbit liver (e.g. guinea-pig kidney and rat caecum both 64 pmol/min/mg; rat liver 0.3 pmol/min/mg), forming 15-keto and 13,14-dihydro-15-keto metabolites as determined by TLC, HPLC and GC/MS. Prostaglandin D2 was not transformed in similar fashion in NAD+- or NADP+-supplemented incubations in any of the 12 cytosolic systems. However, PGD2 was converted to a single product identified by TLC, HPLC and GC/MS as 9 alpha, 11 beta-PGF2 in certain of the systems when supplemented with an NADPH regenerating system, with high activity in guinea-pig kidney (55.0 pmol/min/mg), guinea-pig liver (27.5 pmol/min/mg) and rabbit liver (13.7 pmol/min/mg) and less than 5 pmol/min/mg in 8 of the remaining 9 systems. This stereospecific 11-ketoreductase of rabbit and guinea-pig liver was stable to 10 min heating at 50 degrees, dialysis, storage at -20 degrees and repeated freeze/thawing but was not inhibited by sulphasalazine analogues. The 11-ketoreductase had a markedly different tissue profile from PGE2 9-ketoreductase, which was shown to convert PGE2 stereospecifically to 9 alpha, 11 alpha-prostaglandin F2 (PGF2 alpha) and was present at highest activity in rabbit liver and kidney. Evidence was obtained that 9 alpha, 11 beta-PGF2 was actively transformed by the sulphasalazine-inhitable 15-PGDH pathway at approximately one third of the rate of PGF2 alpha with high activity in several cytosolic systems (e.g. rat caecum, guinea-pig liver and kidney), suggesting that further transformation in vivo of this biologically active product of PGD2 metabolism could be initiated by this route.
Hoult
J R
JR
Department of Pharmacology, King's College (KQC), Strand, London, U.K.
Bacon
K B
KB
Osborne
D J
DJ
Robinson
C
C
D000818:Animals; D001711:Biotransformation; D002432:Cecum / Q000378:metabolism; D015237:Dinoprost / Q000378:metabolism*; D006168:Guinea Pigs; D006911:Hydroxyprostaglandin Dehydrogenases / Q000032:analysis; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008168:Lung / Q000378:metabolism; D008297:Male; D009928:Organ Specificity; D015230:Prostaglandin D2 / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains
D015237:Dinoprost; D006911:Hydroxyprostaglandin Dehydrogenases; C035859:15-hydroxyprostaglandin dehydrogenase; C031051:prostaglandin-F synthase; C035858:prostaglandin-E2 9-reductase; D015230:Prostaglandin D2