Effects of hyperthermia on the membrane potential and Na+ transport of V79 fibroblasts

✍ Scribed by Ross B. Mikkelsen; Craig R. Asher

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 629 KB
• Volume: 144
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041440206

✦ Synopsis

Abstract

The effects of hyperthermia (41–43°C) on the membrane potential (calculated from the transmembrane distribution of [^3^H]tetraphenylphosphonium) and Na^+^ transport of Chinese hamster V79 fibroblasts were studied. At 41°C, hyperthermia induced a membrane hyperpolarization of log phase cells (5 to 26 mV) that was reversible upon returning to 37°C. The hyperpolarization was inhibited 50% by 1 mM ouabain or 0.25 mM amiloride, an inhibitor of Na^+^: H^+^ exchange. Shifting temperature to 41°C increased ouabain‐sensitive Rb^+^ uptake indicating activation of the electrogenic Na^+^ pump. At 43°C for 60 min, the membrane potential of log phase cells depolarized (20–35 mV). Parallel studies demonstrated enhanced Na^+^ uptake at 41°C only in the presence of ouabain. At 43°C, Na^+^ uptake was increased relative to controls with or without ouabain present. At both 41 and 43°C, 0.25 mM amiloride inhibited heat‐stimulated Na^+^ uptake. Na^+^ efflux was enhanced at 41°C in a process inhibited by ouabain. Thus, one consequence of heat treatment at 41°C is activation of Na^+^:H^+^ exchange with the resultant increase in cytosolic [Na^+^] activating the electrogenic Na^+^ pump. At temperatures ≥43°C, the Na^+^ pump is inhibited.