Evidence for two distinct hormone-sensitive [3H]phosphoinositide pools in bovine adrenocortical zona fasciculata/reticularis cells stimulated with angiotensin II.
Bovine adrenocortical cells from the zona fasciculata/reticularis were isolated and their phosphoinositides labelled to a steady state with [3H]inositol in primary culture. Experiments performed on these cells in the presence of Li+ have shown that, over a period of 60 min, angiotensin II (AII; 10(-7) M) stimulated a linear increase in [3H]inositol phosphates that was sustained through the utilization of two hormone-sensitive subpools of prelabelled lipid (30% and 45% respectively), and a rapid resynthesis of [3H]phosphoinositide into one of these pools using cytosolic [3H]inositol. The 30% pool was used immediately on stimulation, and was sustained at a steady-state size of 10-15% during the first 30 min of stimulation through rapid resynthesis using cytosolic [3H]inositol. Only after 30 min, when the cytosolic [3H]inositol was depleted and resynthesis could no longer occur, did the additional 45% pool start to supply further substrate to the phospholipase C, thereby further sustaining the generation of [3H]inositol phosphates. Once this pool was depleted however (by approximately 60 min), [3H]inositol phosphate generation finally ceased. These findings establish the differential use of two metabolically distinct hormone-sensitive pools of phosphoinositide following AII stimulation in bovine adrenocortical cells, events which are dependent upon the availability of cytosolic inositol for phosphoinositide resynthesis.
Bird
I M
IM
University Department of Clinical Biochemistry, Royal Infirmary, Edinburgh, U.K.
Williams
B C
BC
Walker
S W
SW
D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000378:metabolism*; D015383:Zona Fasciculata / Q000166:cytology / Q000378:metabolism*; D015385:Zona Reticularis / Q000166:cytology / Q000378:metabolism*
D010716:Phosphatidylinositols; D000804:Angiotensin II; D008094:Lithium