Possible involvement of intracellular Ca2+ in hyposmosis-evoked catecholamine release from adrenal chromaffin cells

Vinblastine enhancement of hyposmosis-induced catecholamine release in cultured adrenal chromaffin cells: lack of relation to cell swelling and microtubule disruption

Exposure of chromaffin cells to hyposmotic solution has been shown to cause catecholamine release through the elevation of intracellular Ca2+ level. While cell volume change observed under hyposmotic conditions has been shown to be accompanied by the movement of various ions and suggested to be associated with the reorganization of cytoskeletons. In the present study, the effects of cytoskeleton-disrupting agents on hyposmosis-induced catecholamine release were examined to investigate a possible relationship between catecholamine release and cell volume change under hyposmotic conditions. Hyposmosis-induced catecholamine release was enhanced by pre-treatment of the cells with a microtubule-disrupting agent vinblastine, but not significantly altered by a microfilament-disrupting agent cytochalasin B. Vinblastine also caused an additional increase in the intracellular Ca2+ but failed to affect the cell volume change under hyposmotic conditions. In contrast, the hyposmosis-induced release was not significantly altered by either colchicine, another microtubule-disrupting agent, or taxol, a microtubule-stabilizing agent. These results indicate that vinblastine enhances hyposmosis-induced catecholamine release through an additional increase in the intracellular Ca2+ and furthermore suggest that this effect of vinblastine on the hyposmosis-induced release is unassociated with the disruption of the microtubule system, providing evidence for a lack of the direct relationship between catecholamine release and the cell volume change observed under hyposmotic conditions.