Pressure sensitivity of active tension in glycerinated rabbit psoas muscle fibres: effects of ADP and phosphate.

The effect of changes in hydrostatic pressure (up to 10 MPa) on the maximally calcium-activated tension in glycerinated rabbit psoas fibres has been examined. The steady active tension was depressed by 0.8% per MPa pressure rise. This pressure sensitivity was enhanced by the pressure of millimolar phosphate and depressed by millimolar ADP. These results support the conclusions that increased pressure is perturbing a crossbridge event. The results are discussed in terms of a three state crossbridge model and are shown to be compatible with a pressure effect on the transition from an attached crossbridge state to a tension bearing state. This is compatible with the effects of pressure on the isolated proteins in solution.