Bradykinin-stimulated changes in inositol phosphate mass in renal papillary collecting tubule cells.

The effect of bradykinin on changes in the chemical levels of myo-inositol polyphosphates in renal papillary collecting tubules was investigated. Myo-inositol phosphate mass was determined by means of an enzymatic, fluorometric assay. Bradykinin induced increases in myo-inositol mono-, bis-, and trisphosphate which were both time and concentration dependent. Furthermore, the magnitude of the chemical levels of myo-inositol monophosphate formed were unlikely to be accounted for solely by the formation and degradation of myo-inositol trisphosphate. These observations are consistent with the concomitant hydrolysis of phosphatidylinositol and phosphatidylinositol bisphosphate. This study also confirms, in freshly isolated renal tubules, observations regarding bradykinin-induced phosphatidylinositol bisphosphate hydrolysis made previously in radiolabeled cultures.