Objective To investigate changes in uterine contractility and oxytocin receptor (OXTR) level after salt and alkali load in rats during late pregnancy.Methods A total of 42 pregnant rats were randomly divided into groups given tap water (group A),2％ NaCl solution (group B),or 5％ NaHCO3 solution (group C).Two rats were taken from each of the three groups at 0,12,24,36,48,60,and 72 h,respectively,for arterial blood gas analysis and preparation of uterine muscle strips for muscle tension measurement.The OXTR levels were measured using ELISA.Results There were no significant differences in serum sodium and bicarbonate ion concentrations,muscle tension,or OXTR levels among the groups at 0 h (P ＞ 0.05).At other time points,the sodium ion concentration in group B and group C was significantly higher than in group A (P ＜ 0.05),and bicarbonate ion concentration in group C was higher than in group A and group B (P ＜ 0.05).Muscle tension (including amplitude and frequency) in group B was significantly greater than in group A (except at 72 h) (P ＜ 0.05).The amplitude in group C was higher than in group A at 12,24,and 60 h (P ＜ 0.05),while the frequency was higher than in group A at 48,60,and 72 h (P ＜ 0.05).The OXTR level in group B was significantly higher than in group A (P ＜ 0.05),and was higher in group C than in group A at 12,24,60,and 72 h (P ＜ 0.05).Conclusion Salt and alkali loading can increase uterine contractility and OXTR levels at 60 h.