The effects of calcium on glycolysis and ATP concentration in complete and membrane-poor hemolyzates of human erythrocytes.

Hemolyzates prepared from packed human red cells with 30 micrometer total calcium were employed as a means to examine the relationship between ATP consumption and lactate formation. Hemolyzates exposed to ultracentrifugation accumulate membrane fragments in the top layer yielding membrane-poor fractions in the buttom layers of the centrifuge tube. Lactate formation accompanied by ATP depletion amounts to 12 mumoles per ml and hour in complete hemolyzates fortified with NAD. Complexation of calcium results in about 50% inhibition of the lactate formation with a concomitant increase of ATP. Lactate formation is reduced in membrane-poor hemolyzates approximately concurrently to the extent of membrance removal which produces no discernible change in the glyceral-dehydephosphate dehydrogenase activity. 50--200 micrometer total calcium has no effect on the membrane-independent lactate formation which amounts to 1--2 mumoles per ml and hour. Triton X-100 seems to solubilise also the membrane components responsible for the high calcium-dependent ATP consumption which governs the lactate formation.