The Action of Bradykinin and Oxytocin on the Isolated Whole Uterus and Myometrium of the Rat in Oestrus

Abstract

1 A technique is described for obtaining a myometrial preparation devoid of endometrium, from the uterus of the rat in oestrus.2 Acetylcholine and prostaglandin F2a, (PGF2a) produced concentration-effect curves with the same maximal tensions and slope on the whole uterus and myometrial preparations. Concentration-effect curves to bradykinin and oxytocin on the myometrial preparation were altered, resulting in a shift to the right and a decreased maximum response compared with those produced by the whole uterus. 3 Indomethacin produced greater antagonism of the responses of the whole uterus to bradykinin and oxytocin than to acetylcholine and PGF2,, whereas responses of the myometrium to all four agonists were similarly depressed. 4 Responses of the myometrial preparation to a range of concentrations of bradykinin and oxytocin were significantly enhanced by prior sensitization of the myometrium to PGF2,,. This significant enhancing effect of PGF2,, was only seen with the threshold dose of acetylcholine.5 It appears that the mechanism of action of bradykinin and oxytocin on the rat uterus involves both a direct action and an indirect action. The indirect action possibly involves release of prostaglandin(s) from the endometrium.

The epithelium and the pharmacology of guinea‐pig tracheal tone in vitro

“…Contractions produced by one or more of histamine, muscarinic agents, 5-hydroxytryptamine, and K' were slightly increased (either pD2 or E,,, or both) (Flavahan et al, 1985;Barnes et al, 1985;Hay et al, 1986a,b;Raeburn et al, 1986ab;Finnen et al, 1986;Holroyde, 1986), or reduced (this study, cf. Whalley, 1978), or were not affected by epithelium removal (Goldie et al, 1986;Raeburn et al, 1986a, Hay et al, 1986aThompson et al, 1986 and this study). Barnes et al (1985) found that indomethacin did not alter a slightly increased sensitivity to acetylcholine in bovine epithelium-denuded tracheae.…”

“…Despite removal of a large sheet of endometrial epithelial tissue, including a small part of the uterine smooth muscle, this latter tissue responded normally to acetylcholine and prostaglandin F2,. Effects of bradykinin and oxytocin were only slightly reduced in that their maxima were lower in endometriumdeprived preparations (Whalley, 1978). In 1979, Furchgott & Zawadski observed that the vascular endothelial lining was essential for relaxant effects of acetylcholine in vitro.…”

“…However, it seems less likely that epithelial factors would directly affect airway smooth muscle that, similar to the uterine preparation discussed above (Whalley, 1978), is separated from the epithelium by a layer of tissue that is both thicker than the internal elastic lamina, separating endothelial cells from vascular smooth muscle, and contains a very profuse network of microvessels (Sobin et al, 1963;Laitinen et al, 1987). Hence, the airway epithelium may not be comparable to the vascular endothelium as regards possible influence on smooth muscle tone.…”

Prostaglandins and the Contractile Action of Brady‐kinin on the Longitudinal Muscle of Rat Isolated Ileum

“…However the failure of the prostaglandin synthesis inhibitors to reduce contractions to Bk following serosal perfusion is consistent with the findings of Barabe et al (1977) who proposed that Bk had a direct action on longitudinal muscle strips from cat ileum, and segments of rat uterus. A similar dual action for Bk on the rat isolated uterus has been reported by Whalley (1978) who suggested that Bk has a direct action on the myometrium and an indirect action via release of PGLS from the endometrium.…”

Phosphorylation of proteins during human myometrial contractions: A phosphoproteomic approach

“…KNG1 is cleaved to release bradykinin, which is able to stimulate myometrial contractility [21] by stimulating IP3-dependent Ca 2+ release and the bradykinin B2 receptor is expressed in the myometrium at term [22]. Interestingly, the phosphorylation of KANK2 (SRC-1-interacting protein, SIP) by epidermal growth factor has recently been described in human myometrial cells [23].…”