Abstract
Dimethyl sulfoxide (DMSO) initiates a coordinated differentiation program in various cell types but the mechanism(s) by which DMSO does this is not understood. In this study, the effect of DMSO on intracellular calcium ion concentration ([Ca^2+^]~i~) was determined in primary cultures of chicken ovarian granulosa cells from the two largest preovulatory follicles of laying hens, and in three cell lines: undifferentiated P19 embryonal carcinoma cells, 3T3‐L1 fibroblasts, and Friend murine erythroleukemia (MEL) cells. [Ca^2+^]~i~ was measured in cells loaded with the Ca^2+^ ‐specific fluoroprobe Fura‐2. There was an immediate (i.e., within 5 sec), transient, two to sixfold increase in [Ca^2+^]~i~ after exposing all cell types to 1% DMSO. DMSO was effective between 0.2 and 1%. The prompt DMSO‐induced [Ca^2+^]~i~ spike in all of the cell types was not prevented by incubating the cells in Ca^2+^ ‐free medium containing 2 mM EGTA or by pretreating them with the Ca^2+^‐channel blockers methoxyverapamil (D600; 100 μM), nifedipine (20 μM), or cobalt (5 mM). However, when granulosa cells, 3T3‐L1 cells, or MEL cells were pretreated with lanthanum (La^3+^; 1 mM), which blocks both Ca^2+^ channels and membrane Ca^2+^ pumps, there was a sustained increase in [Ca^2+^]~i~ in response to 1% DMSO. By contrast, pretreating P19 cells with La^3+^ (1 mM) did not prolong the DMSO‐triggered [Ca^2+^]~i~ transient. In all cases, the DMSO‐induced [Ca^2+^]~i~ surge was unaffected by pretreating the cells with the inhibitors of inositol phospholipid hydrolysis, neomycin (1.5 mM) or U‐73, 122 (2.5 μM). These results suggest that DMSO almost instantaneously triggers the release of Ca^2+^ from intracellular stores through a common mechanism in cells in primary cultures and in cells of a variety of established lines, but, this release is not mediated through phosphoinositide breakdown. This large, DMSO‐induced Ca^2+^ spike may play a role in the induction of cell differentiation by DMSO. © 1993 Wiley‐Liss, Inc.