The actions of extracellular H+ on the electrophysiological properties of isolated human detrusor smooth muscle cells.

Abstract

1. The influence of extracellular pH changes on intracellular pH and [Ca2+], as well as on L-type Ca2+ currents, has been investigated in isolated human detrusor smooth muscle cells. 2. Alteration of extracellular pH by changing superfusate PCO2 also changed intracellular pH. A change of superfusate pH made by altering the [NaHCO3] at constant PCO2 was not reflected in a change in intracellular pH. 3. Extracellular acidosis attenuated the magnitude and rate of change of intracellular [Ca2+] evoked by raising the extracellular [KCl]. 4. Extracellular acidosis attenuated the rate of rise and amplitude of the action potential, as well as the magnitude of the L-type Ca2+ current. In the pH range 6.78-7.62 no alteration to the voltage dependence of Ca2+ current activation or inactivation was recorded. 5. A close proportional relationship between tension generated by multicellular strips and the magnitude of peak inward Ca2+ current in isolated cells was noted over a wide range of the two variables using a number of interventions, including alteration to extracellular pH, [Ca2+] and [Mg2+]. 6. Extracellular acidosis attenuated the magnitude of caffeine-dependent intracellular Ca2+ transients and the resting [Ca2+]i between transients. Acidosis was without effect on the rise of [Ca2+]i induced by carbachol. 7. The results suggest that the negative inotropic effect of extracellular acidosis can be accounted for by attenuation of the L-type Ca2+ current. The results also imply that intracellular stores are influenced by transmembrane Ca2+ fluxes at rest and that such fluxes are also attenuated by extracellular H+.

• Authors: C H Fry, C R Gallegos, B S Montgomery
• Journal: The Journal of physiology (J Physiol) Vol. 480 ( Pt 1) Pg. 71-80 (Oct 01 1994) ISSN: 0022-3751 [Print] England
• PMID: 7853227 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Calcium Channels
• Carbon Dioxide
• Carbachol
• Potassium
• Calcium

Topics

• Acidosis (physiopathology)
• Action Potentials (drug effects, physiology)
• Calcium (metabolism)
• Calcium Channels (drug effects, metabolism)
• Carbachol (pharmacology)
• Carbon Dioxide (metabolism)
• Electrophysiology
• Extracellular Space (drug effects, metabolism)
• Humans
• Hydrogen-Ion Concentration
• In Vitro Techniques
• Muscle Contraction (drug effects, physiology)
• Muscle, Smooth (cytology, drug effects, physiology)
• Patch-Clamp Techniques
• Potassium (pharmacology)
• Urinary Bladder (drug effects, innervation, physiology)