Ca 2+ release in cultured rat epididymal cells during hypoosmotic swelling

Abstract

Microfluorimetric studies were carried out to investigate the effects of hypoosmotic swelling on intracellular Ca 2+ concentration ([Ca 2+](i)) in single rat epididymal cells. In Ca 2+-free solution containing 50 μmol/l ethylenebis(oxonitrilo)tetraacetate (EGTA) hypoosmotic swelling (-160 mosmol/l) induced a transient rise in [Ca 2+](i)< which was either monophasic, biphasic or oscillatory. The [Ca 2+](i) responses to repeated hypoosmotic stimulations followed a decremental pattern. However, if 2.5 mmol/l Ca 2+ was admitted during the recovery period between successive stimulations, the second and the third [Ca 2+](i) responses were slightly greater than the first. Increasing the change in osmolarity from -14 ± 1.0 to -154 ± 1.5 mosmol/l increased the rise in [Ca 2+](i) but reduced the [Ca 2+](i) response to subsequent ionomycin stimulation (4 μmol/l). The swelling- and the ionomycin-induced rises in [Ca 2+](i) followed a reciprocal pattern. It was suggested that intracellular Ca 2+ release in response to cell swelling in the epididymal epithelium might play a role in cell volume regulation and the control of epididymal fluid osmolarity.