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Developmental changes in intracellular pH buffering power in smooth muscle
A J Bullock1, R A Duquette, N Buttell
1Physiological Laboratory, University of Liverpool, Crown Street, Liverpool L69 3BX, UK.
Insights
Neonatal smooth muscles exhibit distinct buffering capacities compared to adults, influencing their response to pH changes. These developmental differences in buffering power and pH regulation are crucial for understanding tissue function.
Area of Science:
- Physiology
- Developmental Biology
- Biochemistry
Background:
- Intracellular pH (pHi) significantly influences smooth muscle contraction.
- Neonatal tissues may exhibit different contractile responses to stimuli altering pHi compared to adult tissues.
- Buffering capacity (beta) and extracellular pH (pHo) to pHi transmission affect functional responses to pH perturbations.
Purpose of the Study:
- To determine the intrinsic buffering power (beta) in neonatal and adult ureteric, uterine, and gastric smooth muscles.
- To assess the effect of extracellular pH (pHo) changes on intracellular pH (pHi) in these tissues.
- To compare developmental and tissue-specific differences in pH regulation.
Main Methods:
- Utilized the pH-sensitive fluorophore carboxy-SNARF.
- Measured intrinsic buffering power (beta) in isolated smooth muscle tissues.
- Investigated the relationship between extracellular pH (pHo) and intracellular pH (pHi) changes.
Main Results:
- Adult ureteric, uterine, and gastric smooth muscles showed similar buffering power.
- Significant differences in buffering power were observed among neonatal smooth muscle tissues.
- Little difference in the transmission of pHo changes to pHi occurred between neonatal and adult tissues of the same muscle type, but differences existed between muscle types.
Conclusions:
- Significant developmental and tissue-specific differences exist in smooth muscle pH regulation.
- These variations in buffering capacity and pH transmission may influence tissue protection during pH perturbations.
- Understanding these differences is key to explaining varied functional responses in neonatal versus adult smooth muscles.
Abstract:
Intracellular pH (pHi) is known to modulate contraction. Neonatal tissues can differ from adult tissue in contractile response to stimuli known to alter pHi e.g. hypoxia. Changes of pH are attenuated by buffering, thus any difference in buffering power (beta) between tissues could affect their functional response to pHi perturbation. Similarly the extent to which any extracellular pH (pHo) alteration is transmitted into a pHi change will also influence function. We have therefore determined the intrinsic beta and effect of pHo change on pHi in neonatal and adult ureteric, uterine and gastric smooth muscles using the pH-sensitive fluorophore carboxy-SNARF. beta was found to be similar in the three adult tissues, but there were significant differences between neonatal tissues. In contrast, we found little difference in the amount of pHi change produced by pHo change between neonatal and adult tissues from the same smooth muscle, but a difference between smooth muscles. These data highlight significant differences between smooth muscles and their developmental state, which may contribute to different degrees of protection when pH is perturbed.