Similar effects of saponin treatment and aging on coupling of alpha 1-adrenergic receptor-G-protein.
The effects of the nonionic detergent saponin on alpha 1-adrenergic signal transduction were investigated using rat parotid cells and membrane preparations. Fifty microM epinephrine-stimulated 45Ca2+ efflux and inositol 1,4,5-triphosphate (Ins[1,4,5]P3) production in adult parotid cells were significantly decreased after saponin treatment. Saponin did not alter the concentration of alpha 1-adrenergic receptors labeled by [3H]prazosin, but significantly reduced the guanosine imido diphosphate (GppNHp)-induced shift from high to low affinity sites. Fifty microM epinephrine-stimulated high affinity GTPase activity was also reduced by saponin treatment. These data suggest that reduced alpha 1-adrenergic receptor-stimulated functional responsiveness following saponin treatment may be due to impaired uncoupling of receptor-G-protein complexes.
Miyamoto
A
A
Department of Pharmacology, Sapporo Medical College, Japan.
Kowatch
M A
MA
Roth
G S
GS
D000375:Aging / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects; D002478:Cells, Cultured; D004837:Epinephrine / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000096:biosynthesis; D019204:GTP-Binding Proteins / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis; D008297:Male; D010306:Parotid Gland / Q000166:cytology / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects / Q000378:metabolism*; D012503:Saponins / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects
D018340:Receptors, Adrenergic, alpha-1; D012503:Saponins; D015544:Inositol 1,4,5-Trisphosphate; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D002118:Calcium; D004837:Epinephrine