Measurement of sickling by controlled temperature increase

Previous experiments to study the rate of red cell sickling have employed rapid mixing apparatus for SS cells with dithionite and have shown that the half-time of sickling is quite rapid, on the order of seconds. An alternative approach is to slow down the rate by taking advantage of the negative temperature coefficient of the process. We developed a method in which deoxygenation of a cell suspension is carried out at 0 degrees C. A linear temperature gradient to 37 degrees C is applied, and a gradual increase in the percentage of sickled cells is observed. At a heating rate of 1.5 degrees C/min the temperature at which half of the cells became sickled was 19 degrees C for SS cells treated with dithionite, 22 degrees C for SC cells, 28 degrees C for AS cells, 22 degrees C for cyanate-treated SS cells, and 23 degrees C for SS cells in the presence of 0.1 M butylurea. Thus this method promises to be useful for the study of sickling rates and the screening of potential anti-sickling agents.