ISSN:
1440-1681
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
1. The actions of angiotensin II, bradykinin, oxytocin, arginine vasopressin, relaxin, serotonin and the prostaglandins E2 and F2α were examined on preparations of costo-uterine muscle from stilboestrol-treated rats.2. All the agonists, except relaxin, when used in concentrations which contract the rat uterus, also produced contractions of costo-uterine muscles. Concentration-response curves were steep and maximal responses to the agonists were comparable. The negative log molar EC50 values were: serotonin, 6.5; angiotensin II, 8.8; bradykinin, 8.4; PGE2, 8.3; PGF2α, 7.1. The EC50 values (units/L) for oxytocin and vasopressin were 4.4 and 2.7 respectively.3. Indomethacin (2.8 or 5 μmol/L) did not decrease the contractile effects of the peptides or serotonin. The effects of serotonin were reduced, but not reversed, by methysergide (0.94 μmol/L).4. Porcine relaxin inhibited field stimulation-induced contractions of costouterine muscle and uterine horns from immature rats pretreated with oestradiol cypionate and from stilboestrol-treated mature rats. It was much less potent, and its effects were less clearly concentration-related, on costo-uterine muscle.5. The inhibitory effects of relaxin on the uterus were unaffected by propranolol (1 μmol/L), confirming that on this tissue relaxin acts independently of the release of catecholamines. Progesterone (30 μmol/L) was also without effect on the action of relaxin on the uterus.6. These results taken together indicate that the costo-uterine muscle of the rat: (i) contracts in response to serotonin and the peptides angiotensin II, arginine vasopressin, bradykinin and oxytocin independently of the release of the contractile prostaglandins F2α and E2; and (ii) in contrast to the uterus, may lack a significant population of receptors for relaxin. These differences from the whole uterine horn of this species may reflect the absence of endometrial tissue, and/or of sensitivity of the smooth muscle cells of the costo-uterine muscle to oestrogen.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1440-1681.1989.tb01606.x
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