A difference in the cellular mechanisms of secretion of adrenaline and noradrenaline revealed with lanthanum in bovine chromaffin cells.
A comparison of the effectiveness of the trivalent cation, lanthanum (La3+) relative to Ca2+ in causing adrenaline and noradrenaline release from bovine adrenal medullary chromaffin cells has been made. In cells maintained in tissue culture and permeabilised with digitonin, both La3+ and Ca2+ triggered catecholamine release. La3+ was more effective than Ca2+: the EC50 for La3+ was shifted to the left of that for Ca2+ by close to one order of magnitude for both adrenaline and noradrenaline. With respect to adrenaline, the same maximal release was triggered by the two cations, but with respect to noradrenaline, La3+ triggered a significantly greater release than did Ca2+. Mixtures of experimental media containing both La3+ and Ca2+ caused release of adrenaline and noradrenaline in amounts that approximated closely the sum of the releases caused by Ca2+ and La3+ alone. The data strongly imply that either the release mechanisms for adrenaline and for noradrenaline from their respective chromaffin cells are different, or the cellular mechanisms that regulate release from the two cells are different.
Powis
D A
DA
Faculty of Medicine and Health Sciences, The University of Newcastle, New South Wales, Australia.
Clark
C L
CL
D000313:Adrenal Medulla / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D002463:Cell Membrane Permeability / Q000187:drug effects; D004072:Digitonin / Q000494:pharmacology; D004837:Epinephrine / Q000378:metabolism*; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D007811:Lanthanum / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism*
D007811:Lanthanum; D004072:Digitonin; D002118:Calcium; D009638:Norepinephrine; D004837:Epinephrine