Many K+-selective ion channels are present in vascular cells and play an important role in the regulation of vascular tone, including that of coronary vessels. Among them is a class of K+ (KATP) channels that are normally closed at physiological intracellular ATP concentrations (ATPi) but open when ATPi decreases. Basal coronary flow under normal conditions may be tonically controlled by KATP channels. In addition, coronary KATP channels are activated by adenosine released during exercise, hypoxia or ischemia. The channels also constitute the main action site of various drugs. Drugs interacting with the KATP channels may change basal coronary flow under normal conditions. Physiologic regulation of these channels is not fully understood. Protein kinase C (PKC) may modulate coronary flow via an effect on KATP channels. This PKC-mediated modulation may be important, given the role of this enzyme in the signaling pathways mediating the response to neurotransmitters and hormones. Furthermore, since PKC isoform expression and activity can be modified by disease conditions, the enzyme may be partially responsible for pathologic reduction in coronary flow.
Buy this Article