Vasopressin stimulates thromboxane synthesis in isolated hamster hepatocytes: relation to hepatocyte calcium content.

This study was designed to determine if vasopressin stimulates the formation of thromboxane B2 in freshly isolated hamster hepatocytes and if so, whether this thromboxane synthesis plays a role in the vasopressin-induced efflux of 45Ca++ from these cells. Thromboxane synthesis was found to be linear for 15 minutes, to be stimulated by arachidonic acid, and to be inhibited by indomethacin and by 7-(1-imidazolyl) heptanoic acid (7IHA), a selective inhibitor of thromboxane synthetase. Vasopressin stimulation of thromboxane synthesis was dose-related. Pretreatment with 7IHA and meclofenamate significantly increased basal 45Ca++ uptake by the cells. Neither 7IHA nor meclofenamate inhibited the ability of vasopressin to reduce the 45Ca++ content of the isolated hepatocytes. These results indicate that vasopressin stimulates thromboxane synthesis in hepatocytes but suggest that thromboxane does not play a role in the vasopressin-induced reduction in 45Ca++ content in this cell type.