Effects of prostaglandins and oestradiol-17 beta on oxytocin binding in cultured bovine luteal cells.
The aim of the investigation was to evaluate the possible action of prostaglandins (PGs) and oestradiol-17 beta (oestradiol) on the specific binding for oxytocin in bovine luteal cells. Cultured cells of bovine corpora lutea at the mid-luteal stage (Day 8-12 of the oestrous cycle) were examined for the presence of oxytocin receptors by a radioreceptor assay using the 125I-labelled oxytocin antagonist [d(CH2)5,Tyr(Me)2,Thr4,Tyr-NH29]-vasotocin (125I-OVT) as a ligand. The cells were cultured for 48 h in total. In the final 15 h of culture, the luteal cells were exposed to varying concentrations of PGF2 alpha, PGE2 and/or oestradiol. After culture, the cells were incubated with 37,000 dpm (0.5 nM) 125I-OVT with or without 100 nM of unlabelled oxytocin. PGF2 alpha, at 10(-8) M and 10(-7) M, stimulated the specific binding for oxytocin to levels as high as 128% of controls (P < 0.01); by contrast, PGE2, PGI2 or oestradiol had no effect on oxytocin binding. Scatchard analysis revealed that the concentration of oxytocin receptors was increased (P < 0.05) from 6.7 fmol micrograms-1 DNA to 8.4 fmol micrograms-1 DNA by stimulation with 10(-7) M of PGF2 alpha without changing the binding affinity. No further increase in the specific binding was observed when PGF2 alpha was used in combination with PGE2, PGI2 or oestradiol at a concentration of 10(-7) M. Addition of indomethacin (28 microM) resulted in the inhibition of PGF2 alpha secretion, coinciding with a significant decrease in oxytocin binding (P < 0.01). However, addition of arachidonic acid (100 microM) caused a significant increase in the secretion of PGF2 alpha and the specific binding for oxytocin concomitantly (P < 0.05). When the protein kinase C (PKC) activity of the luteal cells was inactivated by preincubating cells for 13 h with 1 microM phorbol 12-myristate 13-acetate before PGF2 alpha stimulation, the specific binding for oxytocin was not affected by PGF2 alpha stimulation (10(-7) M) in the final 15 h of culture. These data suggest that PGF2 alpha may be one of the potent regulators for luteal oxytocin receptors in a paracrine and/or autocrine manner, and that its action is mediated by PKC.
Okuda
K
K
Division of Animal Science and Technology, Faculty of Agriculture, Okayama University, Japan.
Uenoyama
Y
Y
Miyamoto
A
A
Okano
A
A
Schweigert
F J
FJ
Schams
D
D
D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D015237:Dinoprost / Q000494:pharmacology; D015232:Dinoprostone / Q000494:pharmacology; D011464:Epoprostenol / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology*; D004971:Estrus; D005260:Female; D008184:Luteal Cells / Q000187:drug effects / Q000378:metabolism*; D010121:Oxytocin / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011453:Prostaglandins / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism; D011863:Radioimmunoassay; D018045:Receptors, Oxytocin / Q000032:analysis / Q000378:metabolism
D011453:Prostaglandins; D018045:Receptors, Oxytocin; D004958:Estradiol; D010121:Oxytocin; D015237:Dinoprost; D011464:Epoprostenol; D011493:Protein Kinase C; D015232:Dinoprostone