INTRACELLULAR CALCIUM REDISTRIBUTION ACCOMPANIES CHANGES IN TOTAL TISSUE NA-VITRO INCUBATION OF HIPPOCAMPAL SLICES(, K+ AND WATER DURING THE FIRST 2 HOURS OF IN)

Changes of total tissue water, Ca, Na and K contents were monitored in whole transverse hippocampal slices of the guinea-pig during the firs t 2 h of in vitro incubation. A brief, 75% increase in tissue Ca was n oted during the initial IS min of maintenance, in contrast to a perman ent increase of sodium and water contents, coupled to simultaneous dec rease of potassium level. The rate of tissue Na, K and water changes c omprised a rapid phase at the first 10-20 min, parallel with the incre ase of the tissue Ca content, and a slow phase during the rest of the incubation period. Development of specific morphological alterations, representative of ischemic/hypoxic lesions and a translocation of calc ium from cytoplasm to mitochondria and endoplasmic reticulum during sl ice maintenance, was also detected by electron microscopy. A two-step mechanism might explain the development of a new steady-state total ca lcium content of slices, in which the cellular Ca2+ uptake at the begi nning of incubation, likely triggered by hypoxic/ischemic trauma of sl ice preparation, is followed by a balanced Ca2+ influx, extrusion and sequestration (predominantly into mitochondria and endoplasmic reticul um) during maintenance. (C) 1997 IBRO. Published by Elsevier Science L td.