G. Krumschnabel et al., EFFECTS OF ENERGY LIMITATION ON CA2-TOLERANT AND ANOXIA-INTOLERANT HEPATOCYTES( AND K+ HOMEOSTASIS IN ANOXIA), American journal of physiology. Regulatory, integrative and comparative physiology, 42(1), 1997, pp. 307-316
Effects of energy limitation on Ca2+ and K+ homeostasis in anoxia-tole
rant and anoxia-intolerant hepatocytes. Am. J. Physiol. 273 (Regulator
y Integrative Comp. Physiol. 42): R307-R316, 1997.-To gain more insigh
t into the mechanistic basis of anoxia tolerance and intolerance, a co
mparative study was conducted on calcium homeostasis in goldfish and t
rout hepatocytes subjected to different forms of energy limitation. Us
ing the fluorescent Ca2+ indicator fura 2, we observed that both chemi
cal anoxia and true anoxia led to an increase of the concentration of
cytosolic free calcium (Ca-i(2+)) in the anoxia-sensitive hepatocytes
of rainbow trout, whereas Ca-i(2+) was maintained at control levels in
the anoxia-tolerant hepatocytes of goldfish. Various lines of evidenc
e suggest an intracellular origin of the Ca2+ increase observed in tro
ut cells. Cyclosporin A, a specific inhibitor of the mitochondrial per
meability transition pore in mammalian cells, was ineffective in preve
nting the Ca2+ increase, whereas a high dose of fructose depressed the
Ca2+ surge by similar to 50%. The latter effect was not accompanied b
y improvement of the energetic state of the cells. A comparison of che
mical anoxia with true (physiological) anoxia revealed that both treat
ments affected energy metabolism to a similar degree in trout hepatocy
tes, whereas the decrease of ATP seen in goldfish hepatocytes during c
hemical anoxia was absent during true anoxia. Elevation of Ca-i(2+) wi
th the calcium ionophore A-23187 led to a decoupling of unidirectional
K+ fluxes in both normoxic and anoxic trout cells, whereas in goldfis
h hepatocytes the coupling of K+ fluxes was not affected by the rise o
f Ca-i(2+).