ROLE OF CALCIUM IN MITOTIC STIMULATION OF RAT THYMOCYTES BY DETERGENTS AGMATINE AND POLY-L-LYSINE

Low concentrations of the detergents cetyltrimethyl ammonium bromide, dodecyl sodium sulphate, and Triton X-100 stimulate mitotic activity in rat thymocyte populations maintained in vitro. These compounds have no mitotic effect on cells maintained in calcium-free medium. The maximum mitotic activity in the presence of a detergent such as dodecyl sodium sulphate occurs when the CaCl2 concentration is 0.04 mM while the same activity in detergent-free medium occurs only when the CaCl2 concentration is 2.5 mM. Similarly, the organic cations agmatine and poly-l-lysine also stimulated mitosis in calcium-containing medium, but not in calcium-free medium. It is concluded that all these compounds stimulate mitosis only indirectly by sensitising the mitotically competent segment of a thymocyte population to the action of calcium. © 1968.