Decrease of extracellular pH associated with the secretion of catecholamines induced by barium in perfused bovine adrenal medulla.
1. The possible modifications of extracellular pH produced during buffer-free 5 mM Ba2+ stimulation was studied in decorticated perfused bovine adrenal glands. 2. A significant and reversible drop of pH accompanied the release of catecholamines each time the tissue was exposed to a buffer-free 5 mM Ba2+ solution. 3. A progressive declination of the magnitude of this acidification associated with a gradual attenuation of the secretory response was observed consecutive to successive periods of Ba(2+)-stimulation. 4. D-600 (methoxyverapamil), in a concentration of 3 x 10(-4) M, markedly antagonized both Ba(2+)-induced secretory response and extracellular pH drop. 5. Perfusion of adrenal medulla for 4 min period with Locke solution buffered at pH 6.9, significantly and reversibly reduced the secretory response to 5 mM Ba2+ (pH 6.9) compared to a first control response obtained 35 min before at pH 7.4. 6. These results are compatible with the view that Ba(2+)-induced secretory activity is accompanied by the release of protons which could be involved in a local negative automodulatory mechanism of adrenomedullary secretion.
Departamento de Fisiologia, Facultad de Farmacia y Bioquimica, Universidad de Buenos Aires, Argentina.
J E
JE
Pinto
P N
PN
Viglione
R P
RP
Rothlin
C
C
Gomez
D000313:Adrenal Medulla / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D001464:Barium / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D005711:Gallopamil / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D010477:Perfusion
D015220:Calcium Channels; D002395:Catecholamines; D001464:Barium; D005711:Gallopamil