EXTRACELLULAR ACIDIFICATION RELATED TO THE STIMULATION OF CATECHOLAMINES RELEASE BY STRONTIUM IN THE BOVINE ADRENAL-MEDULLA

The possible modifications of extracellular pH associated with the sec retion of catecholamines evoked by the introduction of 2.2 mM Sr2+ to a Ca2+-free, buffer-free, Locke solution were investigated in decortic ated perfused bovine adrenal glands. A progressive and reversible decr ease of external pH accompanied the catecholamine release promoted by Sr2+-introduction into the perfusion fluid. This extracellular acid sh ift was practically undetected when the chromaffin tissue was stimulat ed by the addition of Sr2+ to a buffered medium. Both the secretory re sponse as well as the extracellular pH drop mediated by Sr2+-introduct ion to a Ca2+-free, buffer-free, Locke solution were markedly inhibite d by methoxyverapamil (0.3 mM), Mg2+ (20 mM) and hyperosmolarity (750 mOsm). The exposure of the adrenal medulla to a Ca2+-free, buffer-free , high-K+ solution containing 2.2 mM Sr2+ for 6 min promoted a signifi cant enhancement of both the secretory response and the acidification of the perfusates compared with the responses evoked by Sr2+ in a 5.6 mM K+ medium. These results are consistent with the existence of a clo se relationship between extracellular acidification and the release of catecholamines triggered by the introduction of Sr2+ to the perfusion fluid.