Role of phosphoinositol metabolism and phospholipases C and A2/A1 in signal transduction in isolated rat adrenal cells.

Isolated rat adrenal glomerulosa cells were prelabelled with [3H]inositol and stimulated with 25 nM-angiotensin II in the presence of Li+. The resulting inositol monophosphates were separated using h.p.l.c. and 2 major peaks of radioactivity were detected. These showed the same characteristics as inositol 4-phosphate and inositol 1-phosphate and stimulation with angiotensin II increased activity 4-5 fold and 7-8-fold respectively. A minor peak with the characteristics of inositol 1:2 cyclic phosphate increased 1.5-fold after stimulation. No material corresponding to inositol 2-phosphate or inositol 5-phosphate was detected. The results establish the identify of the main inositol phosphate products in angiotensin II-stimulated rat glomerulosa cells. Analysis by h.p.l.c. has been similarly used to assess the inositol phosphates produced after ACTH1-39-stimulation of isolated rat adrenal fasiculata-reticularis cells. A low dose of ACTH1-39 (10(-12) M) stimulated production of small but significant amounts of both glycerophosphoinositol and inositol monophosphate. Using superfused isolated fasiculata-reticularis cells it was also found that ACTH1-39 (10(-9) M and 10(-12) M) rapidly increased efflux of 45Ca+ from 45Ca2+-prelabelled cells. It is concluded that although the results are consistent with a role for phospholipase C in the action of angiotensin II on adrenal glomerulosa cells, in the action of ACTH on adrenal fasciculata-reticularis cells a role for phospholipase A2/A1 is implicated.