CHANGES IN INTRACELLULAR PH CLOSE TO TERM AND THEIR POSSIBLE SIGNIFICANCE TO LABOR

The contractile pattern of uterine smooth muscle is markedly altered b y even modest manipulations of intracellular pH (pH(i)); an acidificat ion can abolish contractions, while alkalinization increases contracti lity. As at the end of gestation the uterus changes from being relativ ely quiescent to highly contractile, we investigated whether pH(i) cha nges with pregnancy in women. Isolated tissue was loaded with the pH-s ensitive fluorophore, carboxy-SNARF. We found a significant alkaliniza tion over the last few weeks of pregnancy. Such an increase in pH(i) w ill increase contractility of the uterus, and may therefore contribute to the mechanisms ensuring strong and efficient contractions occur du ring labour.