Volume regulation of human peripheral blood lymphocytes and stimulated proliferation of volume-adapted cells.

Human peripheral blood lymphocytes exposed to hypotonic media (Ca/Mg-free, room temp.) first swell and then shrink. This shrinking response is characterized by a simple exponential with a half-time of 1.44 +/- 0.60 min (n = 11) and its extent but not the half-time for a given hypotonicity is influenced by [K+]0. Using K-selective electrodes, we observe a change in [K+]0 when cells are diluted into hypotonic media. A half-time of 1.55 +/- 0.06 min (n = 4) was obtained. A similar half-time was obtained by assay of total cell K using atomic absorption spectroscopy. At all osmolarities [K+]i was decreased from control values and was constant as [K+]0 was increased. Short-term incubation with ouabain (10(-4) M) had no effect. Decreasing osmolarities progressively inhibited phytohemagglutinin-stimulated DNA synthesis, yet cell number and viability remained unaltered. Our evidence indicates that the volume response is mediated by a change in the passive permeability of the plasma membrane to K and/or to the accompanying anions, and that the consequently volume-adapted cells are growth-inhibited.