OSMOTIC EFFECTS ON PLASMA-MEMBRANE OF THYMOCYTES

Rat thymocytes were treated with media of different hypotonic osmolarity and the resulting damage of the plasma membrane was monitored by measuring the permeation of biochemical markers (K+, fluorescein, lactate dehydrogenase) and by observation of morphological changes in the plasma membrane using the freeze-etch technique. Release is dependent on the molecular weight of the markers; those with higher molecular weights permeate predominantly at a lower osmolarity of the medium and those with lower molecular weights permeate at a higher osmolarity. The marker release is temperature dependent: at 4°C it takes place at a lower osmolarity of the medium than at 37°C. With decreasing osmolarity of the medium at 4°C a decrease in the number of the intramembranous particles and increasing aggregation of the intramembranous particles occurs. © 1978.