[Alterations of cardiac Gi protein alpha subunits during ischemia-reperfusion in rats]

Alteration of G proteins in rat heart during ischemia-reperfusion was studied. Levels of Gi alpha 2, Gi alpha 3 and Gs alpha in sarcolemma and light vesicle were measured by Western blot analysis. Adenyl cyclase activities were determined by radioimmunoassay. During ischemia-reperfusion, cardiac function parameters were decreased significantly. Expressions of Gs alpha remained unchanged. Compared with the control group, levels of Gi alpha 2 and Gi alpha 3 in sarcolemma in ischemia-reperfusion group increased by 37.4% (P < 0.01) and 42.4% (P < 0.01), respectively with, however, no changes in light vesicle; Activities of adenyl cyclase decreased during ischemia-reperfusion. The results suggested that the increased expression of cardiac Gi may contribute to the dysfunction of adenyl cyclase signal transduction system and the impaired cardiac function during ischemia-reperfusion.