Response of human fibroblasts to hypertonic stress. Cell shrinkage is counteracted by an enhanced active transport of neutral amino acids

• Published in: The Journal of biological chemistry 1994-04, Vol.269 (14), p.10485-10491
• Main Authors: Dall'Asta, V, Rossi, P A, Bussolati, O, Gazzola, G C
• Format: Article
• Language: English
• Subjects: Adolescent; Amino Acids - metabolism; Biological and medical sciences; Biological Transport, Active; Cell morphology; Cell Size; Cells, Cultured; Fibroblasts - cytology; Fibroblasts - metabolism; Fundamental and applied biological sciences. Psychology; Humans; Hypertonic Solutions; Male; Membrane Potentials; Molecular and cellular biology; Osmolar Concentration; Potassium - metabolism; Protein Biosynthesis; Sodium - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(17)34085-1

Regulatory volume increase (RVI) has been studied in cultured human fibroblasts (CHF) incubated in a complete hypertonic growth medium (400 mosmol/kg). After the initial cell shrinkage induced by hypertonic treatment, cells recover their volume almost completely within 3 h. This RVI response is associated with a marked increase of the cell content of free amino acids. The cell content of potassium increases only slightly. Chromatographic analysis of the intracellular amino acid pool shows that the RVI-associated increase in cell amino acids is mainly a result of changes in the L-glutamine content. The intracellular accumulation of the analog 2-methylaminoisobutyric acid, a specific substrate of transport system A, is increased in CHF undergoing RVI. Hypertonic treatment causes an immediate and sustained cell hyperpolarization, as demonstrated by changes in the trans-membrane distribution ratio of L-arginine and in the fluorescence of the potential-sensitive dye bis-1,3-diethylthiobarbiturate-trimethineoxonol. Because of cell hyperpolarization, at the end of RVI the trans-membrane gradient of the sodium electrochemical potential is higher than that of the control. The increase in the extracellular potassium concentration ([K+]out = 40 mM) abolishes the hyperpolarization induced by hypertonic treatment and delays volume recovery. Cycloheximide suppresses RVI at a high but not at physiologic [K+]out. It is proposed that CHF counteract hypertonic shrinkage through an enhanced accumulation of substrates of transport system A sustained, initially, by an increase in the energy available for transport and, subsequently, also by the synthesis of new site A carriers.