Human fibroblasts shrink and are unable to recover their initial volume when incubated in hypertonic saline solutions, whereas an efficient volume restoration takes place in hypertonic media containing substrates of the highly concentrative transport system A (amino acids and methylamines). Amino acid substrates of barely concentrative transport systems are ineffective in sustaining the volume recovery. The activity of system A increases following incubation of fibroblasts under conditions promoting cell shrinkage and decreases upon cell swelling. These results stress the role of system A in the regulation of cell volume. Adaptive changes in the activity of system A are also induced by cell starvation and refeeding (adaptive regulation). Cell starvation is associated with cell shrinkage, while cell refeeding is accompanied by cell swelling. It is suggested that nutritional regulation and cell volume control by system A may be part of a common regulatory network. © 1991 S. Karger AG, Basel.
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