Effects of energy limitation on Ca2+ and K+ homeostasis in anoxia-tolerant and anoxia-intolerant hepatocytes

KRUMSCHNABEL G, SCHWARZBAUM PJ, BIASI C, DORIGATTI M, WIESER W

AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY, INTEGRATIVE AND COMPARATIVE PHYSIOLOGY

AMER PHYSIOLOGICAL SOC

Año: 1997 p. 307 - 316

0363-6119

tolerance and intolerance, a comparativestudy was conducted on calcium homeostasis in goldfish andtrout hepatocytes subjected to different forms of energylimitation. Using the fluorescent Ca2+ indicator fura 2, weobserved that both chemical anoxia and true anoxia led to anincrease of the concentration of cytosolic free calcium (Caa’)in the anoxia-sensitive hepatocytes of rainbow trout, whereasCaf+ was maintained at control levels in the anoxia-toleranthepatocytes of goldfish. Various lines of evidence suggest anintracellular origin of the Ca2+ increase observed in troutcells. Cyclosporin A, a specific inhibitor of the mitochondrialpermeability transition pore in mammalian cells, was ineffectivein preventing the Ca2+ increase, whereas a high dose offructose depressed the Ca2+ surge by -50%. The latter effectwas not accompanied by improvement of the energetic state ofthe cells. A comparison of chemical anoxia with true (physiological)anoxia revealed that both treatments affected energymetabolism to a similar degree in trout hepatocytes,whereas the decrease of ATP seen in goldfish hepatocytesduring chemical anoxia was absent during true anoxia.Elevation of Car+ with the calcium ionophore A-23187 led to adecoupling of unidirectional K+ fluxes in both normoxic andanoxic trout cells, whereas in goldfish hepatocytes the couplingof K+ fluxes was not affected by the rise of Caf’.goldfish; rainbow trout; adenosinetriphosphate; lactate;