Fig. 1.
The effect of brief hypoxic episodes in rat myometrium, HIFI. (A) Paired data (i) control uterine contractions and (ii) multiple brief hypoxic episodes (Nitrogen, N2) produce increased contractility (HIFI). (B) Increased contractility produced by hypoxia is maintained for many hours. (C) The protocol produced 2% oxygen saturation. (D–F) Brief application of three hypoxic episodes to (D) term-pregnant (TP), (E) 18-d pregnant, and (F) nonpregnant myometrium. (G and H) The effect of brief hypoxic episodes (G) in the presence of oxytocin (OT) and (H) in the presence of the oxytocin receptor antagonist, atosiban. Note that the effects of HIFI are independent of oxytocin. (I) Mean force amplitude after the third hypoxic episode at different gestational stage. *P < 0.05, in comparison with the control. Statistical analysis was performed using Bonferroni one-way ANOVA. All error bars show mean ± SEM.