Effect of hydrostatic pressure on isolated cardiac nuclei: Stimulation of RNA polymerase II activity.

RNA polymerase activity was measured in isolated cardiac nuclei subjected to hydrostatic pressure. After 20 min of pressure, Mn2+ stimulated RNA polymerase II activity was increased. The response to pressure was inhibited by low concentrations of alpha-amanitin (1.1 microgram.cm-3) an inhibitor of polymerase II activity. The data show that pressure applied to isolated nuclei stimulates RNA polymerase II activity, forming mRNA, and suggests that direct application of pressure to cardiac nuclei may be the stimulus which triggers the augmented protein synthesis seen in pressure overload.