Regulation of bovine cervical secretion of prostaglandins and synthesis of cyclooxygenase by oxytocin.
Prostaglandin E2 (PGE2) can cause softening of the bovine cervix at oestrus when receptors for oxytocin (OT) are maximally present, indicating a relationship between OT and PGE2 production. It was therefore determined whether OT can stimulate prostaglandin synthesis or induce cyclooxygenase expression in cervical external os segments obtained from pre-oestrous-oestrous cows. Tissues were minced and incubated (50-100 mg mL[-1] 6 h[-1]) in the presence of OT (10 ng mL[-1]), progesterone (P4) (5 ng mL[-1]) and/or indomethacin (5 microg mL[-1]). It was found that OT stimulated basal PGE2 (7.79+/-1.22 ng 100 mg[-1], mean+/-s.e.m.; n = 6) in external os segments from pre-oestrous-oestrous cows (P < 0.03), whereas P4 and indomethacin inhibited basal and OT-stimulated PGE2 production (P < 0.05). Basal prostaglandin F2alpha (PGF2alpha) production was minimal (<1 ng 100 mg[-1]) and OT had no effect on its production. Expression of cyclooxygenase was measured by Western blot analysis following incubation of the tissue (100 mg 1.5 mL[-1] 3 h[-1]) in the presence of OT (10 ng mL[-1]) and in the presence of P4 (5 ng mL[-1]). It was found that OT stimulated the induction of cyclooxygenase II (79+/-10%; n = 7, P < 0.05). In contrast, P4 inhibited the basal expression of this enzyme (-40+/-5%, n = 7, P < 0.05) in the presence or absence of OT. It is concluded that, in vitro, OT stimulates PGE2 synthesis by the bovine cervix at oestrus and that this effect is mediated by cyclooxygenase.
Shemesh
M
M
Department of Hormone Research, Kimron Veterinary Institute, Bet Dagan, Israel. shemesh@agri.huji.ac.il
Dombrovski
L
L
Gurevich
M
M
Shore
L S
LS
Fuchs
A R
AR
Fields
M J
MJ
D000818:Animals; D015153:Blotting, Western; D002417:Cattle / Q000378:metabolism* / Q000502:physiology; D002584:Cervix Uteri / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D015331:Cohort Studies; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D015237:Dinoprost / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects; D004971:Estrus / Q000378:metabolism; D005260:Female; D007213:Indomethacin / Q000494:pharmacology; D010121:Oxytocin / Q000494:pharmacology*; D011374:Progesterone / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis* / Q000187:drug effects
D016861:Cyclooxygenase Inhibitors; D011374:Progesterone; D010121:Oxytocin; D015237:Dinoprost; D011451:Prostaglandin-Endoperoxide Synthases; D015232:Dinoprostone; D007213:Indomethacin