Prostaglandin catabolism in the bovine placenta

The enzymes responsible for the metabolism of prostaglandins in bovine placenta

The following review presents some data on the enzymes of synthesis and catabolism of prostaglandins in bovine placenta. The available literature confirms the anabolic and catabolic ability of bovine placenta to metabolise prostaglandins, but there is little direct information about the pathways involved. The aim of the review is to describe what is known about the physico-chemical properties and activity of enzymes involved in prostaglandin metabolism in bovine placenta.

Prostaglandin E2 9-keto reductase from bovine term placenta

The aim of the following study was to determine the activity and physico-chemical properties of prostaglandin E2 9-keto reductase from bovine placenta. Placental tissues obtained immediately after parturition were subjected to purification procedure consisting of homogenization, affinity chromatography, gel filtration and allowed to electrophoresis. The activity of enzyme was measured spectrophotometrically. The purification procedures receive 135-fold purified enzyme preparate of the molecular weight of 45 kDa with the following kinetic values: Michaelis constant for PGE2, 117 microM and max velocity 183 pmol/min. The activity of enzyme was also detected with 20 alpha-hydroxypregn-4en-3-one and with 9,10-phenanthrenquinone (Michaelis constant 22 microM and 6 microM, respectively). The determination of physico-chemical properties of prostaglandin E2 9-keto reductase, performed for the first time in bovine placenta, should aid the understanding of the metabolism of prostaglandins and their biological importance in physiological and pathological conditions in cattle.

15-Hydroxy-prostaglandin dehydrogenase activity in uterine tissues of late gestational and parturient cows

15-Hydroxy-prostaglandin dehydrogenase activity (PGDH) was measured in endometrium, allanto-chorion, allanto-amnion and the placenta from six cows during late gestation and six parturient cows during caesarean section. Under saturated substrate conditions PGDH activity was lower than 138 pmol g wet tissue-1 min-1 in all uterine tissues in both groups. Human placental reference samples showed a PGDH activity of 16,800 +/- 1200 pmol per g wet weight min-1 (n = 4). Under subsaturational conditions enzyme activity was demonstrated in endometrium and both fetal membranes. These results indicate that PGF2 alpha catabolism in bovine uterine tissue on day 262 and during parturition, contributes little to changing plasma PGFM concentrations.

Circulating PgF2α and nutritional parameters at parturition in dairy cows with and without retained placenta: Relation to prepartum diet

Reproductive and biochemical parameters were studied at parturition in multiparous single-carrying Holstein cows. These were compared in animals with (n=14) and without (n=40) a retained placenta and then according to 2 prepartum diets (corn silage/concentrate, n=44; grass silage/concentrate, n=10) in cows with and without retained placentas. Cows with retained placentas had a 4-day shorter gestation period and gave birth to 5 kg-lighter calves than cows without retained placentas. Furthermore, their plasma PGFM -PgF2alpha main metabolite- (3325 vs 5675 pg/ml; P<0.01) and glucose (79.2 vs 95.2 mg/100ml; P<0.05) levels were lower and their protein concentration was higher (85.7 vs 76.5 g/l; P<0.05) than those of cows without retained placentas. Retained placenta incidence in cows fed grass-silage was higher than in cows fed corn-silage (60% vs 18.2%; P<0.05). Cows with retained placentas and fed corn silage had shorter gestation lengths, gave birth to lighter calves, and had less circulating glucose at calving (77.6 vs 96.5 mg/100ml; P<0.05) than cows without retained placentas and fed the same forage. Cows with retained placentas and fed grass silage had less PGFM (2172 vs 4530 pg/ml; P<0.05) than cows without retained placentas and fed the same forage. Calving number, sex ratio and preceeding milk yield were not different between the two groups of cows whatever their prepartum diet. In the dairy cow, retained placenta could be due to a PgF2alpha or an energy deficiency at calving. Roles of the dietary polyunsaturated fatty acids toward the Pg synthesis and of the energy supply before calving in relation to retained placenta are discussed here.

Arachidonic acid metabolism by bovine placental tissue during the last month of pregnancy

Conversion of tritiated arachidonic acid (AA) into metabolites of the cyclo- and lipoxygenase pathways by bovine fetal placental tissue (200 mg) and fetal plus maternal placental tissue (400 mg) of Days 255, 265, 275 of gestation and at parturition (n = 5) during a 30 min incubation was measured using reverse-phase high pressure liquid chromatography. Fetal placental tissue produced 13,14-dihydro-15-keto-prostaglandin E2 (PGEM) as the major metabolite, the synthesis of which increased from Day 265 to Day 275 and parturition by 150% and 475%, respectively. In tissues collected at parturition, PGE2 synthesis was also detected. On Day 275 and at parturition fetal placental tissue synthesized the metabolite 12-hydroxyheptadecatrienoic acid (HHT), and throughout the experimental period the lipoxygenase product 15-HETE was detected with synthesis rates increasing over time of gestation. In addition, an unidentified metabolite was regularly found in the radiochromatograms which eluted at 1 h and 1 min (U101), between HHT and 15-HETE. The synthesis of this metabolite decreased as pregnancy progressed. Furthermore, various other polar and nonpolar metabolites pooled under the heading UNID were eluted, the production of which increased over time of gestation. The presence of maternal placental tissue did not influence the synthesis of PGEM, 15-HETE and U101, but the production of HHT was decreased when maternal tissue was present. Also, as pregnancy progressed, maternal placental tissue seemed to contribute to the pool of unidentified metabolites. In conclusion, fetal placental tissue seems to be the major source of the AA metabolites when compared with maternal placental tissue, and AA metabolism by bovine placental tissue is markedly increased throughout the last month of pregnancy, suggesting a role for AA metabolites in mechanisms controlling parturition.