Increase in concentration of uterine oxytocin receptors and decrease in response to 13,14-dihydro-15-keto prostaglandin F2 alpha in ewes after withdrawal of exogenous progesterone.
Ovariectomized ewes were treated with progesterone and oestradiol to induce oestrus (day of expected oestrus = day 0) and with progesterone on days 1 to 12. The concentrations of endometrial oxytocin receptors and the 13,14-dihydro-15-keto prostaglandin F2 alpha (PGFM) response induced by oxytocin were measured on days 12, 14, 16 and 18 after the cessation of progesterone treatment on day 12, by a receptor binding assay and direct radioimmunoassay, respectively. During the period of treatment, the concentrations of plasma progesterone were high and remained above 2 ng ml-1 until day 13 when they dropped rapidly to less than 0.5 ng ml-1 by day 14. The concentrations of oxytocin receptors in endometrium of control ewes were high (820.7 +/- 91.7 (SEM) fmol mg-1 protein). Treatment with progesterone significantly (P < 0.01) reduced the concentrations of the receptors on days 12 and 14 (144.1 +/- 65.0 and 200.4 +/- 45.4 fmol mg-1 protein, respectively). The receptor concentrations then increased to relatively high values on day 16 (1021.4 +/- 216.6 fmol mg-1 protein) and remained high until day 18 (677.7 +/- 103.4 fmol mg-1 protein).(ABSTRACT TRUNCATED AT 250 WORDS)
Lau
T M
TM
Victorian Institute of Animal Science, Werribee, Victoria, Australia.
Kerton
D J
DJ
Gow
C B
CB
Fairclough
R J
RJ
D000818:Animals; D015237:Dinoprost / Q000031:analogs & derivatives* / Q000378:metabolism; D004717:Endometrium / Q000378:metabolism; D005260:Female; D010052:Ovariectomy; D010121:Oxytocin / Q000378:metabolism* / Q000494:pharmacology; D011374:Progesterone / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology; D011945:Receptors, Angiotensin / Q000378:metabolism*; D018045:Receptors, Oxytocin; D012756:Sheep / Q000097:blood / Q000378:metabolism*; D014599:Uterus / Q000187:drug effects / Q000378:metabolism*
D011945:Receptors, Angiotensin; D018045:Receptors, Oxytocin; C008228:15-keto-13,14-dihydroprostaglandin F2alpha; D011374:Progesterone; D010121:Oxytocin; D015237:Dinoprost