Suppression of cytoplasmic Ca2+ response and protein secretion by oxidizing agents.

The influence of the oxidizing agents (H2O2, KO2 and Vitamin K) on the action of vasopressin to guinea pig hepatocytes was investigated from the view-point of cytoplasmic Ca2+ concentration and protein secretion. 10 nmol/l vasopressin brought about increase in prothrombin secretion along with increase in the cytoplasmic Ca2+ concentration compared to the non-stimulation level. The pretreatment of the cells with 1 mumol/l of the oxidizing agents, however, led to suppression of Ca2+ elevation and inhibited the vasopressin-induced prothrombin secretion completely, while no leak if lactic dehydrogenase (LDH), Na+ and K+ were detected. The same results of the inhibition in fibrinogen and albumin secretion were observed. These results suggested a possibility that the oxidizing agents such as the peroxides act on some site of cellular signal transduction system in cell membrane to reduce the cytoplasmic Ca2+ level and to suppress the vasopressin-induced secretion.