Figure 4. The effects of lactate on pH_i in myometrial smooth muscle .

A, typical example of the effects of 5 mM sodium lactate and butyrate on pH_i measured in the same preparation of rat myometrium. Tissues loaded with carboxy‐SNARF and calibrated using nigericin. B, effects of increasing concentrations of lactate on pH_i. C, simultaneous recording of force (top) and pH_i (bottom) comparing the effects of 5 mM lactate, in the same preparation, showing its effects on spontaneous and oxytocin stimulated contraction. Note the smaller induced pH change and greatly reduced effect on force when oxytocin is present. D, simultaneous application of lactate and NH₄Cl (5 mM) ‘null’ most of the change in pH and prevent the decrease in force previously shown with lactate application. In (C) and (D), the notches on the pH traces are a result of the transient changes in pH_i that occur with contraction (Taggart & Wray, 1993).