The kinetics and thermodynamics of lysis of young and old sheep red blood cells.

The kinetics of heat-induced lysis of a population of sheep red blood cells over the temperature range 42 degrees - 56 degrees C are shown to be similar in form to the survivorship curves of multicellular organisms and are describable by the power law function,--(1/N)(dN/dt) = At(n-1). The A parameter of the power law function is examined in this model system in an attempt to show its relationship to molecular events. Arrhenius-type plots of the A parameter are different for old populations of red blood cells compared to young populations. The plot for the old cells shows a high energy transition at 50 degrees C. For the young cells an activation enthalpy of 232 kcal/mole is obtained with no transition occurring at 50 degrees C. The parameter l/tau, defined as A1/n, is more directly related to the molecular basis of the temperature dependence of the lysis kinetics. The Arrhenius plots of 1/tau give activation enthalpies of 42.8 and 40.4 kcal/mole for young and old cells, respectively, and activation entropies of 57.6 and 50.3 cal/mole per degree. These activation enthalpies and activation entropies appear to be in accord with a compensation law for these qualities for protein denaturation, and support the suggestion that protein denaturation is the rate-limiting step in the lysis of sheep red blood cells.