Polyphosphoinositide metabolism in adrenal glomerulosa cells.

We examined the effect of angiotensin II, a calcium-mobilizing hormone on polyphosphoinositide metabolism in isolated rat adrenal glomerulosa cells. In cells preloaded with [32P]phosphate or with [3H]inositol, stimulation with angiotensin resulted in an approx. 40% reduction in the radioactivity of triphosphoinositide (PtdIns4,5P2) within 15 s. Only a slight increase in radioactivity was observed in the subsequent 30 min. Changes in labelling of diphosphoinositide (PtdIns4P) showed similar kinetics. Incorporation studies also showed a reduction in the pool size of [32P]PtdIns4P and [32P]PtdIns4,5P2 in response to angiotensin. Production of inositol phosphates in the absence or presence of lithium, a cation-inhibiting myo-inositol-1-phosphatase, was examined in cells preloaded with [3H]inositol. The results indicate that the production rate of inositol tris- and bisphosphate shows a manifold increase in the first seconds of stimulation and remains enhanced for at least several minutes. The present data suggest that the rate of resynthesis of polyphosphoinositides also increases shortly after the activation of PtdIns4,5P2 phosphodiesterase. Corticotropin, a hormone acting via cyclic AMP, neither affected polyphosphoinositide metabolism nor modified the action of angiotensin II.