Roles of alpha-2-adrenergic receptor isoforms in inflamed pig uterus contractility in vitro.

Noradrenergic control is very significant for the contractility of healthy and inflamed uteri. The receptor mechanisms of noradrenaline (NA) influencing the contractile activity of an inflamed uterus are poorly recognized. This study was undertaken to determine the participation of α2-adrenergic receptors (ARs) isoforms (A, B, C) in NA-evoked contractility of the pig uterus with severe acute endometritis. Saline (SAL group) or E.coli suspension (E.coli group) were injected into uterine horns, while only laparotomy was performed in the CON group. In relation to the period before NA application, NA decreased the tension, amplitude and frequency in the uterine strips of the CON and SAL groups, and the amplitude and frequency in the E.coli group. In the E.coli group, the amplitude and frequency were lower than in other groups. Compared to NA effect alone, a greater reduction or appearance of a decrease in the amplitude and frequency were noted in all groups following the use of selective α2A- and α2C-ARs antagonists together with NA as well as in the tension in the CON and SAL groups in response to an α2C-ARs antagonist and NA. Such effects were also exerted by an α2B-ARs antagonist with NA on the frequency in all groups and on the amplitude in the CON and SAL groups. To sum up, in an inflammatory-changed porcine uterus, three α2-AR isoforms mediate the effect of NA on contractile frequency, while α2A- and α2C-AR are involved in the control of contractile amplitude. These results could offer new targets for drugs against decreased uterine contractility in inflammation.