DEVELOPMENTAL-CHANGES IN INTRACELLULAR PH BUFFERING POWER IN SMOOTH-MUSCLE

Intracellular pH (pH(i)) is known to modulate contraction. Neonatal ti ssues can differ from adult tissue in contractile response to stimuli known to alter pH(i) e.g. hypoxia. Changes of pH are attenuated by buf fering, thus any difference in buffering power (beta) between tissues could affect their functional response to pH(i) perturbation. Similarl y the extent to which any extracellular pH (pH,) alteration is transmi tted into a pH(i) change will also influence function. We have therefo re determined the in trinsic beta and effect of pH(0) change on pH(i) in neonatal and adult ureteric, uterine and gastric smooth muscles usi ng the pH-sensitive fluorophore carboxy-SNARF. beta was found to be si milar in the three adult tissues, but there were significant differenc es between neonatal tissues. In contrast, we found little difference i n the amount of pH(i) change produced by pH(0) change between neonatal and adult tissues from the same smooth muscle, but a difference betwe en smooth muscles. These data highlight significant differences betwee n smooth muscles and their developmental state, which may contribute t o different degrees of protection when pH is perturbed.