title: Potassium and taurine release are highly correlated with regulatory volume decrease in neonatal primary rat astrocyte cultures.
abstract: Neonatal rat primary astrocyte cultures were swollen by exposure to hypotonic buffer. Using an electrical impedance method for determination of cell volume coupled with on-line measurements of efflux of radioactive ions or amino acids, we have investigated the role of K+ (using 86Rb), taurine, and D-aspartate (an analogue of glutamate) in regulatory volume decrease (RVD). Addition of 1 mM quinine, 10 microM nimodipine, 100 microM BAPTA-AM, 10 microM trifluoperazine, or a calcium-free buffer significantly (p < 0.0001) inhibited RVD. This was accompanied by inhibition of 86Rb release but an increase in D-[3H]-aspartate release, which was proportional to the degree to which RVD was inhibited. These results support a regulatory role for calcium in RVD and show that inhibition of calcium entry from the extracellular fluid, intracellular calcium sequestration, inhibition of calcium-activated K+ channels, and inhibition of calmodulin all inhibit RVD. Because D-[3H]aspartate efflux profiles increase as RVD is inhibited, it is unlikely that D-aspartate release is a main determinant of RVD. In contrast, [3H]taurine release was increased by 1 mM quinine and inhibited by 10 microM trifluoperazine. The net release of K+ and taurine is highly correlated with the degree of RVD, implicating a regulatory role for both K+ and taurine release in RVD.
authors.affiliation: Department of Pharmacology and Toxicology, Albany Medical College, New York 12208.
authors.forename: D
authors.initials: D
authors.lastname: Vitarella
authors.forename: D J
authors.initials: DJ
authors.lastname: DiRisio
authors.forename: H K
authors.initials: HK
authors.lastname: Kimelberg
authors.forename: M
authors.initials: M
authors.lastname: Aschner
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001224:Aspartic Acid / Q000378:metabolism; D001253:Astrocytes / Q000166:cytology* / Q000502:physiology*; D002118:Calcium / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D007038:Hypotonic Solutions; D009553:Nimodipine / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D011803:Quinine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012414:Rubidium Radioisotopes; D028021:Sodium-Potassium-Chloride Symporters; D013654:Taurine / Q000378:metabolism*; D014268:Trifluoperazine / Q000494:pharmacology
chemical_list: D002352:Carrier Proteins; D007038:Hypotonic Solutions; D012414:Rubidium Radioisotopes; D028021:Sodium-Potassium-Chloride Symporters; D013654:Taurine; D014268:Trifluoperazine; D001224:Aspartic Acid; D004533:Egtazic Acid; D009553:Nimodipine; D011803:Quinine; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D011188:Potassium; D002118:Calcium