Optimal efficiency of human platelet shape changes.

The light scattering extinction coefficients and kinetic rate constant(s) for the disc to sphere and the sphere to (smaller) 'spiny sphere' shape changes induced in platelets by saturating amounts of ADP are compared at 31, 37 and 41 degrees C. Platelets exhibit optimum efficiency at 37 degrees C, as judged by not only the rates of the shape changes but also by alterations in the overall sizes and shapes of the three platelet forms. Unstimulated (discoid) platelets appear to be flatter at 37 degrees C, the disc to sphere reaction appears to be impaired at other than 37 degrees C, and the pseudopodia which characterize the final spiny sphere may be more prominent at 41 degrees C.