Regulation of Calcium Channels in Vascular Smooth Muscle

Abstract

Most contractile responses of vascular smooth muscle are dependent on Ca entry, as indicated by the absence or the reduction of the responses when tissues are bathed in solution devoid of Ca. At rest, Ca influx across the plasma membrane is about 20 nmol Ca/g tissue per minute. Opening of Ca channels in the plasma membrane causes a rapid increase of Ca influx resulting from the large electrochemical gradient existing between the extra- and intracellular compartments (1). Different molecular structures appear to ensure Ca movement across the plasma membrane. In addition to their typical electrical properties, the L subtype of voltage-operated Ca channels (VOCs) can be distinguished from other types of Ca channels by their sensitivity to Ca agonists and antagonist dihydropyridines. We have investigated whether, besides the control exerted by membrane potential, VOC activity could be regulated by agonists and intracellular messengers in vascular smooth muscle cells.