Influence of D₂O on Resistance of Plant and Animal Cells, Cellular Models and Actomyosin to some Denaturing Agents

Abstract

ACCORDING to the denaturation theory of injury^1,2 the response of a cell to the effect of various agents is determined by conformational changes induced in macromolecules of protoplasmic proteins. In seeking to define conditions which would increase the resistance of various proteins to denaturing influences and to determine their effect on the stability of living cells, our attention was directed to the influence of D₂O on proteins. Deuterization increases the resistance to heating in certain proteins, such as ribonuclease³, gelatin⁴, collagen⁵ and keratin⁶. We investigated the effect of D₂O on resistance to heating and high hydrostatic pressure in plant (leaf epidermis of Campanula persicifolia L.) and animal (ciliated epithelium of the palate in the frog Rana temporaria) cells on one hand, and in protein preparations (muscle actomyosin of frogs and glycerin models of frog ciliated cells⁷) prepared according to Hoffmann-Berling⁸, on the other. The following resistance indices of cells and proteins were studied in the media containing D₂O (test) or H₂O (control): (a) the temperature at which 5-min heating irreversibly stopped protoplasmic streaming in plant cells; (b) the hydrostatic pressure which, after 5 min, stopped protoplasmic streaming in the same cells; (c) the minimal pressure which, after 5 min, stopped protoplasmic streaming in the plant cells; (d) the temperature at which ciliary movement of the frog cells ceased after 5 min or 1 sec heating; (e) the hydrostatic pressure which stopped ciliary movement after 5 min; (f) the degree of suppression of actomyosin ATPase activity after 15-min heating at 40° C; (g) the degree of suppression of actomyosin ATPase activity after 15 min at 1,300 atm.; (h) the temperature at which, after 5 min, the movement of glycerin models of ciliated epithelium in the presence of ATP is prevented. We also investigated the influence of the duration of the contact between D₂O and cells, cellular models and actomyosin, on their resistance to heating and high hydrostatic pressure. The results were as follows:.