DEUTERIUM-OXIDE (HEAVY-WATER) ACCELERATES ACTIN ASSEMBLY IN-VITRO ANDCHANGES MICROFILAMENT DISTRIBUTION IN CULTURED-CELLS

While deuterium oxide (D2O) is known to produce various biological eff ects in living animals and cultured cells, the detailed mechanisms by which it does so remain unclear. The present study was designed to ass ess the effects of D2O on microfilaments (MFs) via fluorescence staini ng of BALB 3T3 cells and in vitro actin polymerization studies, After BALB 3T3 cells had been exposed to a concentration of more than 30% D2 O for several hours, stress fibers in the peripheral region became thi ck and distinct, while the quantity of perinuclear MFs was drastically reduced, This effect was transient and returned to the original distr ibution within 12 h. Cytoplasmic F-actin (FA) also increased transient ly coincident with the enhancement of stress fibers, The pattern of ce ll locomotion became simpler, and total locomotor activity was suppres sed in a D2O concentration-dependent manner. Analysis of in vitro stud ies demonstrated that, when purified G-actin was polymerized in D2O at a concentration greater than 10%, the rate of actin polymerization wa s accelerated, whereas the total amount of polymerized actin at the st eady state in D2O was the same as that in H2O controls, A gelation ass ay and transmission electron microscopy (TEM) showed that the network of crosslinked FA with alpha-actinin became denser in 30% D2O than in H2O. These findings concerning actin polymerization and FA gelation su ggest that the alteration of stress fibers in cultured cells is caused by a direct effect of D2O on cellular MF dynamics.