Effects of Ursolic Acid on Contractile Activity of Gastric Smooth Muscles

Abstract

Ursolic acid (UA) in concentrations of 1×10⁻⁷ mol/L - 5×10⁻⁵ mol/L induced relaxation in gastric smooth muscle (SM) tissues, in a concentration-dependent manner. The relaxation did not change membrane potential and slow wave contraction patterns. A significant decrease in amplitude and frequency of spike-potentials was observed. UA-induced reactivity was removed when SM preparations were treated with nifedipine (1×10⁻⁶ mol/L). Ca²⁺- induced contractions of the depolarized SM preparations (42 mmol/L K⁺; Ca²⁺- free Krebs solution) were substantially reduced in the presence of UA. It was determined that, in certain concentrations, UA influenced L – type Ca²⁺ channels, and reduced the Ca²⁺ influx.