The possible implication of membrane-associated actin in stimulus-secretion coupling in adrenal chromaffin cells

Chromaffin cells of the bovine adrenal medulla were fused with liposomes containing DNAaseI. Resting membrane potential measurements, obtained by the use of the cyanine dye diS-C₃ (5), showed that DNAaseI incorporation causes depolarization from −56 to −31 mV, which is similar to that induced by ouabain. The level of basal secretion which occurs after the introduction of DNAaseI is increased several fold. Actin filaments, which can be depolymerized by DNAaseI, thus appear to be involved in stimulus-secretion coupling in chromaffin cells. It is suggested that plasma membrane-associated microfilaments control the Na⁺-K⁺-pump and/or the permeability of Ca²⁺ ions thus affecting the membrane potential as well as secretion.