Angiotensin II and guanine nucleotides stimulate formation of inositol 1,4,5-trisphosphate and its metabolites in permeabilized adrenal glomerulosa cells.
Angiotensin II (AII) interacts with specific receptors in the adrenal glomerulosa cell and stimulates the hydrolysis of plasma membrane phosphoinositides by phospholipase C, with production of inositol 1,4,5-trisphosphate (Ins-1,4,5-P3) and subsequent mobilization of intracellular Ca2+. In electrically permeabilized, [3H]inositol-labeled glomerulosa cells, AII stimulated Ins-1,4,5-P3 production within 15 s with half-maximal potency of 10(-9) M. The nonhydrolyzable GTP analog, guanosine 5'-O-thiotriphosphate (GTP gamma S), stimulated Ins-1,4,5-P3 formation in a dose-dependent manner with half-maximal effect at 10(-7) M. AII-activated Ins-1,4,5-P3 production was further increased by guanine nucleotides. The rate at which GTP gamma S-stimulated inositol polyphosphate production was consistently slower than that of AII. In adrenal membrane preparations, GTP gamma S-stimulated polyphosphoinositide hydrolysis was enhanced by Ca2+, with half-maximal activity at 300 nM free Ca2+. Ins-1,4,5-P3 formation was also increased by NaF, further indicating the involvement of a guanine nucleotide regulatory protein. In addition to Ins-1,4,5-P3 and its metabolites formed during degradation via the 4-monophosphate pathway, AII and GTP gamma S stimulated the formation of the phosphorylated metabolite inositol 1,3,4,5-tetrakisphosphate and inositol 1,3,4-trisphosphate in permeabilized cells. The absence of a significant rise in inositol 1-monophosphate indicated that phosphatidylinositol hydrolysis was not stimulated by AII or GTP gamma S. Pretreatment of glomerulosa cells with pertussis toxin for 12 h before permeabilization did not inhibit AII- or GTP gamma S-stimulated inositol polyphosphate formation. However, treatment with cholera toxin, forskolin, or 8-Br-cAMP for 12 h enhanced both basal and ligand-stimulated Ins-1,4,5-P3 production. These observations suggest that agonist binding to the AII receptor activates a polyphosphoinositide-specific phospholipase C in the adrenal glomerulosa cell, and that a distinctive guanine regulatory protein is involved in this mechanism.
Baukal
A J
AJ
Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, Bethesda, Maryland 20892.
Balla
T
T
Hunyady
L
L
Hausdorff
W
W
Guillemette
G
G
Catt
K J
KJ
D000302:Adrenal Cortex / Q000187:drug effects* / Q000378:metabolism; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D002463:Cell Membrane Permeability; D002772:Cholera Toxin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D006150:Guanine Nucleotides / Q000494:pharmacology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000378:metabolism*; D037342:Pertussis Toxin; D012969:Sodium Fluoride / Q000494:pharmacology; D013403:Sugar Phosphates / Q000378:metabolism*; D013873:Thionucleotides / Q000494:pharmacology; D013997:Time Factors; D010738:Type C Phospholipases / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D006150:Guanine Nucleotides; D007295:Inositol Phosphates; D013403:Sugar Phosphates; D013873:Thionucleotides; D010566:Virulence Factors, Bordetella; D000804:Angiotensin II; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D015544:Inositol 1,4,5-Trisphosphate; D006160:Guanosine Triphosphate; D012969:Sodium Fluoride; D002772:Cholera Toxin; D037342:Pertussis Toxin; D010738:Type C Phospholipases; D002118:Calcium