Peripheral blood lymphocytes display reduced K+ channel activity in aged humans

Steady-state parameters of whole-cell K+ current have been determined in human peripheral blood lymphocytes of young (20-50 y.) and elderly (> 90 y.) volunteers by patch-clamp. The magnitude and voltage dependence of the K+ conductance were similar in both lymphocyte populations. The midpoint of steady-state inactivation was -53.3 +/- 2.3 mV for lymphocyte population of young individuals and -65.0 +/- 3.0 mV for that of elderly, showing a significant shift to hyperpolarized potentials. The peak of the steady-state open probability of the K+ channels was decreased and shifted to depolarized potentials by approx. 12.5 mV for lymphocytes of elderly donors. It is suggested that the observed differences in the K+ current parameters may be at least partly responsible for the impaired responsiveness of elderly lymphocytes to proliferative stimuli.