Key Points
- To examine the voltage sensitivity of intracellular pH and assess membrane proton permeability in rat mesenteric vascular smooth muscle cells during potassium-induced depolarization.
- Loaded rat mesenteric resistance vessel strips with the fluorescent indicator SNARF-1 to measure intracellular pH while simultaneously recording mechanical tension at 37 °C and pH 7.4.
- Depolarized tissue strips using isosmotic substitution of potassium for sodium under physiological conditions, in calcium-free solutions, and with intracellular pH regulation pharmacologically blocked.
- High-potassium depolarization elicited tissue contraction alongside transient intracellular alkalinization, which persisted unchanged when standard pH regulatory mechanisms were blocked.
- Omission of extracellular calcium prevented contraction and resulted in significantly greater high-potassium-induced alkalinization compared to preparations in 3 mM calcium.
- Proton influx dynamics and mathematical modeling demonstrated voltage-sensitive proton channel behavior, yielding an estimated membrane proton permeability of 0.4 cm s^-1.
Structured PICO
PPopulationStrips of rat mesenteric resistance vessels (vascular smooth muscle cells) loaded with SNARF-1
IInterventionHigh-K+ depolarization (isosmotic substitution of K+ for Na+)
CComparatorBaseline conditions and nominally Ca2+-free solution versus 3 mM Ca2+
OOutcomeIntracellular pH (pHi) and tissue tensionsurrogate
The study demonstrates a voltage sensitivity of intracellular pH in mesenteric vascular smooth muscle cells and a particularly high permeability of the membrane to protons.