Distension Influences Responses to Agonists and Potassium in Several Types of Small Artery

Excitation-contraction coupling mechanisms in vascular smooth muscle were classically subdivided into i) electro-mechanical coupling which through depolarisation of the cell membrane opens voltage operated calcium channels and induces contraction through the influx of calcium and ii) pharmaco-mechanical coupling which via receptor activation evokes the influx of calcium, release of calcium from intracellular stores and sensitises the contractile apparatus for calcium (1). Many vascular responses, however, can not solely be explained by either of these mechanisms. Examples of these include the myogenic response to pressure increases (2), flow and stretch induced responses (3, 4) and on a longer term basis effects of flow and pressure on vascular structure (5). What these responses have in common is that they are initiated by a mechanical stimulus. A perturbation of the strain and stress is sensed, transduced and translated into a cellular response. The mechanisms by which this is achieved are still subject of intense research.