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Intracellular pH: effect on pulmonary arterial smooth muscle
1Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis 46202.
The American Journal of Physiology
|June 1, 1991
Summary
Changes in intracellular pH (H+) affect pulmonary arterial tone. Intracellular alkalosis causes contraction, while acidification triggers transient contraction via calcium channels, impacting lung blood flow.
Area of Science:
- Physiology
- Pulmonary Circulation
- Smooth Muscle Physiology
Background:
- Pulmonary arterial tone regulation is crucial for maintaining blood flow through the lungs.
- The role of intracellular pH (H+) in modulating pulmonary arterial smooth muscle contraction is not fully understood.
Purpose of the Study:
- To investigate the direct effects of altered intracellular H+ concentration on pulmonary arterial smooth muscle tone.
- To elucidate the mechanisms by which intracellular alkalosis and acidification influence pulmonary arterial contraction.
Main Methods:
- Isolated canine intrapulmonary arteries were exposed to varying concentrations of ammonium chloride (NH4Cl).
- Intracellular pH ([H+]i) and tension were measured simultaneously.
- Experiments were conducted in calcium-free media and with specific inhibitors (nifedipine, ryanodine) to probe mechanisms.
Main Results:
- Ammonium chloride induced contraction in intrapulmonary arteries, primarily through intracellular alkalosis.
- Intracellular alkalosis stimulated contraction directly and via intracellular calcium release.
- Intracellular acidification triggered a transient, nifedipine-sensitive contraction, suggesting extracellular calcium influx through voltage-gated channels.
Conclusions:
- Modifications in intracellular pH significantly affect pulmonary arterial smooth muscle tone.
- Intracellular alkalosis directly stimulates contraction, while acidification induces transient contraction via calcium influx.
- These pH-mediated changes in tone can alter pulmonary blood flow.