Cooling and Response to Histamine in Calf Cardiac Vein

In the present work we studied the responses of calf cardiac vein to histamine (10-9-3x10-4M) and effects of moderate cooling (to 28 °C) on these responses with analysis of the role of endothelial mediators and K+ -ions. Concentration-response curves to histamine were isometrically recorded at 37 and 28 °C (control). The same procedure was repeated at 28°C in the presence of NG-nitro-L-arginine methyl ester (L-NAME, 10-4 M), indomethacin (10-5 M), and also in the K+-free medium. During cooling, the sensitivity, but not the maximal response, was significantly lower than 37 °C. Cooling to 28°C after treatment with L-NAME did not modify the effect of cooling, whereas treatment with indomethacin increased, significantly. Furthermore, cooling to 28 C after incubation in K+-free solution increased the sensitivity to histamine. The results of this study suggest the role of cyclooxygenase pathway and also K+ ions in the cooling-induced changes of calf cardiac vein treated with histamine.