[Effect of nicotine on uterine blood flow and antagonistic effect of prostaglandin I2 derivative (OP-41483) in pregnant ewes].

In order to elucidate the mechanism of the detrimental effect of smoking on uteroplacental circulation in pregnant women, and to confirm the protective effect of PGI2 derivative (OP-41483) against the effect, hemodynamic responses to various doses of nicotine infusion (0.25-1.0 mg/min) were measured before and during the OP-41483 infusion in chronically instrumented pregnant ewes. Moreover, the isometric tension responses of spiral strips of sow uterine arteries to the nicotine and norepinephrine perfusion were also measured using an in vitro technique. The results were as follows: Maternal mean arterial blood pressure (MAP) and the cardiac output were increased by the intravenous infusion of various doses of nicotine; however the uterine blood flow (UBF) decreased consistently in a dose-dependent fashion, and it decreased 20.4% from the control level following the infusion of 1.0 mg/min nicotine, suggesting a detrimental effect on the fetus. During the infusion of OP-41483 (25 micrograms/min), nicotine induced MAP increases were suppressed at all test doses and the decrease in UBF was lessened by 22% of control delta UBF on doses of 1.0 mg/min nicotine. In the muscle chamber, the tension increase in uterine artery strips of nonpregnant sows to various nicotine concentrations (10(-7)-10(-4) M) were suppressed by the preliminary treatment with phentolamine (0.1 mg/min), and the responses to norepinephrine were also suppressed by the preliminary treatment with a low concentration of nicotine (10(-6) M) in the buffer bath.(ABSTRACT TRUNCATED AT 250 WORDS)