THE RESPONSE OF SMOOTH MUSCLE IN DIFFERENT IONIC ENVIRONMENTS

Abstract

The response of uterine horns from virgin guinea pigs to pituitary extract obtained from acetone-extracted pars posterior was determined in varying ionic environment. Concentration of standard solution, in mM. per liter: Na, 144.0; K, 6.2; Mg, 1.0; Ca, 0.53; Cl, 122.0: HC03, 30.0; H2PO4-HPO4, 1.0. pH, 7.40, determined colorimetrically. Increase of K or Ca ion, and large increases in phosphate, increases the response to pituitary. Decrease or increase of Mg, and removal or decrease of Ca, decreases the response. Lowering the pH by varying CO2 or bicarbonate ions increases the response, while rise of pH, similarly produced, decreases the response. Rise of COa ion decreases activity, lowering increases. Variation of pH, CO3 being constant, has no effect on response. Substitution of 50% of all ions by sucrose reduces response. Total substitution by sucrose and phosphate or sucrose and NaOH increases response.