EFFECT OF HYPEROSMOLARITY ON EXTRACELLULAR ACIDIFICATION ASSOCIATED WITH CATECHOLAMINE SECRETION EVOKED BY BARIUM IN PERFUSED BOVINE ADRENAL-MEDULLA

1. The effects of the increase of osmotic strength on extracellular pH modifications produced during buffer-free, 5 mM Ba2+ stimulation was studied in decorticated perfused bovine adrenal glands. 2. A pronounce d and reversible attenuation of the extracellular pH drop as well as o f the release of catecholamines induced by Ba2+ was detected in glands exposed to a hyperosmotic (750 mOsm) perfusion fluid made up by the a ddition of NaCl. 3. Similar results were observed using sucrose as osm oticant instead of NaCl. 4. A progressive decline in both external aci dification and secretory response to Ba2+ was found on gradually incre asing the osmotic strength of the perfusion fluid. 5. These results pr ovide additional evidence in favour of the existence of a close associ ation between extracellular acidification and adrenomedullary secretio n induced by buffer-free Ba2+.