Effects of NaCl removal on osmolyte fluxes and regulatory volume decrease in cultured astrocytes

✍ Scribed by O. Quesada; E. González; S. Morales-Mulia; J. Bargas; H. Pasantes-Morales

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 151 KB
• Volume: 53
• Category: Article
• ISSN: 0360-4012
• DOI: 10.1002/(sici)1097-4547(19980715)53:2<195::aid-jnr8>3.0.co;2-2

✦ Synopsis

Cultured cerebellar astrocytes exhibit regulatory volume decrease (RVD) after anisosmotic swelling by extrusion of potassium (K), chloride (Cl), and organic osmolytes. The volume decay curve after swelling in 50% hyposmotic solutions has a first-order rate constant k min -1 of 0.18 and 70% cell volume recovery is attained after 15 min. Replacing NaCl in the hyposmotic medium by sugars and polyalcohols markedly accelerated RVD increasing k to 0.37-0.39 min -1 and full recovery in 3-5 min. NaCl removal increased (80%) K efflux (measured as 86 Rb), delayed the inactivation of Cl efflux (measured as 125 I) and enhanced taurine and D-aspartate release by 25%. These effects appear due to NaCl removal rather than to specific actions of the organic molecules. Replacing Na by other cations or Cl by gluconate increased k to 0.22 min -1 and 0.26 min -1 , respectively, and 86 Rb efflux by 4-23% and 39, respectively. It is concluded that the electrochemical gradient after NaCl removal increasing the K driving force, delaying the equilibrium of Cl and increasing amino acid efflux, accounts for the observed RVD acceleration. Other consequences of NaCl removal possibly modulating the K efflux pathway include changes in the surface charge screening, decreased ion strength, a rise in [Ca] i and a decrease in intracellular Na.