Histamine evoked sustained elevations of cytosolic Ca2+ in bovine adrenal chromaffin cells independently of Ca2+ entry.
Whole-cell patch-clamp experiments and optical measurements with the Ca2+ fluorescent dye fura-2 were performed to examine histamine induced cytosolic Ca2+ changes in bovine adrenal chromaffin cells. The purpose of this study was to find out whether the sustained plateau phase, which followed the rapid transient increase, was due to Ca2+ influx. The extracellular Ca2+ dependence appeared to be minor, because substitution of Ca2+ with EGTA or BAPTA did not cause obvious changes in the biphasic Ca2+ response. Application of histamine in a Mn2+ containing external solution did not quench the fura-2 signal. It was neither possible to detect a histamine induced depolarisation, nor a Ca2+ permeable current. Changing the driving force for Ca2+ during the plateau phase did not result in a correlating fura-2 signal. Metal ions like Cd2+, La3+ and Co2+ which are known to block Ca2+ influx were unable to abolish the typical histamine induced Ca2+ response. These results suggest that primarily intracellular Ca2+ was responsible for generating the characteristic biphasic Ca2+ response due to histamine in bovine adrenal chromaffin cells.
Bödding
M
M
Max-Planck-Institut for biophysikalische Chemie, Abteilung für Membranbiophysik, Göttingen, Germany. mboeddi@gwdg.de
D000818:Animals; D001030:Apamin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002417:Cattle; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D019439:Chromaffin Cells / Q000187:drug effects* / Q000378:metabolism; D003592:Cytophotometry; D004305:Dose-Response Relationship, Drug; D005456:Fluorescent Dyes / Q000378:metabolism; D016257:Fura-2 / Q000378:metabolism; D006632:Histamine / Q000494:pharmacology*; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D011738:Pyrilamine / Q000494:pharmacology; D013997:Time Factors
D002614:Chelating Agents; D005456:Fluorescent Dyes; D006634:Histamine H1 Antagonists; D001030:Apamin; D006632:Histamine; D011738:Pyrilamine; D002118:Calcium; D016257:Fura-2