Osmolarity-sensitive release of free amino acids from cultured kidney cells (MDCK).
The amino acid pool of MDCK cells was essentially constituted by alanine, glycine, glutamic acid, serine, taurine, lysine, beta-alanine and glutamine. Upon reductions in osmolarity, free amino acids were rapidly mobilized. In 50% hyposmotic solutions, the intracellular content of free amino acids decreased from 69 to 25 mM. Glutamic acid, taurine and beta-alanine were the most sensitive to hyposmolarity, followed by glycine, alanine and serine, whereas isoleucine, phenylalanine and valine were only weakly reactive. The properties of this osmolarity-sensitive release of amino acids were examined using 3H-taurine. Decreasing osmolarity to 85, 75 or 50% increased taurine efflux from 0.6% per min to 1.6, 3.5 and 5.06 per min, respectively. The time course of 3H-taurine release closely follows that of the regulatory volume decrease in MDCK cells. Taurine release was unaffected by removal of Na+, Cl- or Ca2+, or by treating cells with colchicine or cytochalasin. It was temperature dependent and decreased at low pH. Taurine release was unaffected by bumetanide (an inhibitor of the Na+/K+/2Cl- carrier); it was inhibited 16 and 67 by TEA and quinidine (inhibitors of K+ conductances), unaffected by gadolinium or diphenylamine-2-carboxylate (inhibitors of Cl- channels) and inhibited 50% by DIDS. The inhibitory effects of DIDS and quinidine were additive. Quinidine but not DIDS inhibited taurine uptake by MDCK cells.
Sánchez Olea
R
R
Institute of Cell Physiology, University of Mexico, Mexico City.
Pasantes-Morales
H
H
Lázaro
A
A
Cereijido
M
M
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000596:Amino Acids / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002460:Cell Line; D003078:Colchicine / Q000494:pharmacology; D003571:Cytochalasin B / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009994:Osmolar Concentration; D015221:Potassium Channels / Q000378:metabolism; D011802:Quinidine / Q000494:pharmacology; D013654:Taurine / Q000378:metabolism; D013696:Temperature; D014882:Water-Electrolyte Balance
D000596:Amino Acids; D015220:Calcium Channels; D015221:Potassium Channels; D013654:Taurine; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D003571:Cytochalasin B; D011802:Quinidine; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D003078:Colchicine