Dilatation of the right atrium stimulates phosphatidylinositol turnover.

1. Dilatation of the rat right atria caused a stimulation of the phosphatidylinositol turnover pathway as measured by an increase in the accumulation of inositol phosphates in isolated, perfused hearts. 2. In right atria, increases were detected after 1 min dilatation and maximal increases were observed after 10 min. Dilatation for 10 min caused an increase in inositol monophosphate inositol bisphosphate and inositol trisphosphate from 23.3 +/- 0.9, 15.4 +/- 0.4, and 9.5 +/- 0.3 (mean and s.e.m., n = 7 ct/min per mg tissue) to 74.6 +/- 2.3, 20.2 +/- 1.3 and 13.6 +/- 1.5 (n = 8), respectively (P less than 0.01 for all inositol phosphates.) 3. These results show that the myocardium can respond to dilatation by an activation of the phosphatidylinositol turnover pathway.