Cyclic AMP-induced depolarization measured by bis-oxonol fluorescence in bovine adrenal medullary chromaffin cells.
Effects of cyclic AMP on membrane potentials were examined by measuring the changes of bis-oxonol fluorescence in bovine adrenal medullary chromaffin cells. 8-Bromo cyclic AMP (8Br-cAMP) or forskolin caused a gradual and long lasting increase of the fluorescence intensity. The effects of 8br-cAMP was blocked by cyclic AMP-dependent protein kinase inhibitor, adenosine-3', 5'-cyclic monophosphothioate, Rp-diastereomer (Rp-cAMPS) and there was no further increase in the fluorescence by 8br-cAMP in the cells depolarized with 56 mM KC1 or gramicidin D. Ouabain or the removal of extracellular K+ ([K+]0 free) which block Na+, K+-ATPase also increased the fluorescence. The effect of 8br-cAMP on the fluorescence was counteracted by ouabain or [K+]0 free and was blocked in the absence of extracellular Na+ but not by tetrodotoxin or the removal of Ca2+ from the medium. These results may suggest that cyclic AMP causes the membrane depolarization by accumulating Na+ through the inhibition of Na+, K+-ATPase in adrenal chromaffin cells.
Minami
N
N
Department of Pharmacology, Hiroshima University School of Dentistry, Japan.
Morita
K
K
Suemitsu
T
T
Miyasako
T
T
Dohi
T
T
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000313:Adrenal Medulla / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D002478:Cells, Cultured; D002838:Chromaffin System / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D005453:Fluorescence; D005456:Fluorescent Dyes; D008564:Membrane Potentials / Q000187:drug effects; D010042:Ouabain / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism; D013858:Thiobarbiturates
D005456:Fluorescent Dyes; D013858:Thiobarbiturates; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; C025284:bis(1,3-diethylthiobarbiturate)trimethineoxonol; D010042:Ouabain; D011189:Potassium Chloride; D012964:Sodium; D000242:Cyclic AMP; D000254:Sodium-Potassium-Exchanging ATPase