In many cell types studied, the regulatory volume increase following a hypertonicity-induced cell shrinkage is known to involve the conductive uptake of inorganic osmolytes as one of the key mechanisms. The present study aimed to characterize a possible shrinkage-activated membrane current in Ehrlich-Lettre-Ascites tumour cells (ELA). Membrane currents were monitored in single ELA by means of the conventional, fast whole-cell patch-clamp method.
After exposure to a 16%-hypertonic medium, 62% of all cells tested (n=162) responded with the activation of an inward current (234 ± 32 pA), an accompanying decrease of cell input resistance, and a shift of the reversal potential from -40.0 mV to 0.3 ± 2.0 mV. This current was reversibly blocked by the ion channel inhibitors (in order of potency) benzamil > gadolinium > amiloride > EIPA. Ion substitution experiments revealed that the current could be carried with almost equal efficiency by Na+, K+ or Li+, whereas it declined completely with NMDG+ or choline+ as the substitute. The data presented show consistently that in ELA cells shrinkage activates a non-selective cation conductance with a pharmacology differing from other volume-activated conductances.
(This abstract is as it is in the printed issue of the journal).