In vitro Uterotonic Effects of Ethanolic Fruit Extract of Picralima nitida (Stapf) on Isolated Uterine Smooth Muscles of Rats.

Abstract

Effects of aqueous ethanolic fruit extract of Picralima nitida (EFEPN) on uterine contractility were investigated using rat model. Uterine muscle strips were harvested from sexually mature non-gravid female rats weighing 200-250 g. In each experiment, strip of about 1cm was mounted in a 35ml organ bath containing Krebs' physiological salt solution, connected to an isometric electronic force displacement transducer and an oscillograph. The following drugs were used as receptor agonists or antagonist: Verapamil (0.02 - 0.2 mol), Salbutamol (0.2 mol), Isoprenaline (0.1 mol), Adrenaline (9.1 nmol), Propranolol (1.0 mol), and Prazosin (10.0 nmol). Both the extract and the standard drugs were applied at concentrations corresponding to the final bath concentration. The extract was found to induce a dose-dependent myometrial contraction at concentrations ranging from 0.035-0.28 mg/ml, whereas concentrations above this range caused a progressive relaxative effect on the uterine muscle tissue. The effective concentrations (EC50) were 0.056 mg/ml and 1.06 mg/ml for contractile and the relaxative responses respectively. The extract did not elicit any contractile response in a physiological salt solution devoid of calcium ions. The contractile response evoked by a fixed concentration of the extract (0.07 mg/ml) decreased as the concentration of verapamil (0.02-0.2 mol) increased. The extract (0.07 mg/ml) did not restore the spontaneous myometrial contraction previously abolished by adrenaline (9.1 nmol) and a selective β-adrenergic receptor agonist, salbutamol (0.2 mol) respectively. However, about 26.3% contraction was observed when a non-selective β-adrenergic stimulant, isoprenaline (0.1 mol) was added simultaneously with the extract. Also, propranolol (0.3 mol) potentiated the contractile response of this extract. Again, when -adrenoceptors of the uterine tissue were selectively blocked by prazosin (10 nmol), the extract did not produce any contractile effect. From this study, it was concluded that EFEPN has the capacity to induce myometrial contraction at a lower concentration, possibly through mobilization of extracellular calcium ions and stimulation of the -adrenoceptors Keywords Picralima nitida, myometrium, contraction