Cell Biology International Reports, Vol. 7, No. 3, March 1983 237 REDUCTION OF Ca 2+ UPTAKE INDUCED BY IONOPHORE A23187 OF RED CELLS FROM MALARIA (PLASMODIUM BERGHEI)-INFECTED MICE Jerapan Krungkrai and Yongyuth Yuthavong Department of Biochemistry, Faculty of Science, Mahidol University, Rama VI Rd., Bangkok, Thailand ABSTRACT &+ The Ca2+ ionophore A23187 has much less capacity to induct! uptake of red cells from P. berghei-infected mice than of ccl:-s from normal mice. The reduction in Ca2+ uptake occurs in both unin-. fected and infected cells at all stages in the infected blood, as shown from experiments with cells separated on colloidal silica density gradient. Measurement of the ionophore concentration in the medium reveals that the ionophore is partitioned into red cell:: from infected blood to a greater extent than cells from normal blood. The reduction in A23187-induced Ca2+ uptake may be due to difference in the interaction of red cell membrane with the -iono- phore, and its already high Ca2+ permeability. INTRODUCTION There is accumulating evidence that malaria infection iclads tc alterations in Ca2+ transport across red cells (Bookchin t c z'., 1981; Tanabe et aZ, 1982; ieida et al, 1981; Krungkrai and Y\lth:i- vong, 1982). These alterations could furthermore be related witi; alterations in monocationic status (Dunn, 1969) and other metat‘oli: alterations. Since the ionophore A23187 binds with Ca2+ and ten equilibrate it across biological membranes (Reed and Lsrdy, -972: Pressman, 1976; Reed, 1?79), including red cell membrane (Ret:d, 1976; Ferreira and Lew, 15'76; Szasz et aZ, 1978), it is of il:tr:rrsi. to know the effect of this ionophore on the Ca2+ status in m::laria-- infected red cells. This report shows that A23187 is much ltsss effective in inducing Ca2+ uptake of red cells from ?. ber3hc !- infected mice than of red cells from normal mice. This chan;,e is not due to inability of the ionophore to be partitioned into infected red cells, but probably due to difference in interaction ki the ionophore with membranes and change in the Ca2+ status o! the red cells in infection, including the increase in membrane C,s2' permeability. 0309--1651'83!030237-08/$03.00:0 0 1983 Academic Pressinc. (London) Ltd