Effect of exercise and thermal stress on subcutaneous protein transport

Radioiodinated albumin was injected into the subcutaneous tissue of the thigh of human subjects and its disappearance rate from the injection site and the blood levels of the tracer were compared between exercise loaded, heat loaded experiments and the control utilizing two-compartment analysis. The time course of radioactivity in the blood was expressed as the equation p(t) = A(e-alpha t - e-beta t). In the exercise experiment, the half-time of beta and the time required to reach the maximum level was significantly shorter than in the heat experiment and in the controls. The decay of radioactivity at the injection site was set to the equation s(t) = Be-gamma t + Ce-delta t by the least square method. The value of gamma, which had a half-time of about 24 hr, was significantly shorter in the exercise than in the control experiments. From these results, it was concluded that the rate of mobilization of subcutaneous protein via lymph flow is faster under an exercise load than the control, and that the rate under heat load does not deviate from control experiments.