title: Response of human fibroblasts to hypertonic stress. Cell shrinkage is counteracted by an enhanced active transport of neutral amino acids.
abstract: 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.
authors.affiliation: Istituto di Patologia Generale, Università degli Studi di Parma, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Dall'Asta
authors.forename: P A
authors.initials: PA
authors.lastname: Rossi
authors.forename: O
authors.initials: O
authors.lastname: Bussolati
authors.forename: G C
authors.initials: GC
authors.lastname: Gazzola
mesh_terms: D000293:Adolescent; D000596:Amino Acids / Q000378:metabolism*; D001693:Biological Transport, Active; D048429:Cell Size; D002478:Cells, Cultured; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D006982:Hypertonic Solutions; D008297:Male; D008564:Membrane Potentials; D009994:Osmolar Concentration; D011188:Potassium / Q000378:metabolism; D014176:Protein Biosynthesis; D012964:Sodium / Q000378:metabolism
chemical_list: D000596:Amino Acids; D006982:Hypertonic Solutions; D012964:Sodium; D011188:Potassium