Pertussis toxin inhibits noradrenaline accumulation by bovine adrenal medullary chromaffin cells.
Bovine adrenal medullary chromaffin cells maintained in tissue culture accumulated [3H]-noradrenaline by a high affinity, Na(+)-dependent, desipramine-sensitive process. The accumulation was linear with time (1-90 min) and had an apparent Km of 0.52 +/- 0.24 mumol/l and Vmax of 1.70 +/- 0.48 pmol/(10(5) cells.15 min). Pretreatment of the cells with the ADP-ribosylating agent pertussis toxin resulted in a reduction in the Vmax [0.81 +/- 0.39 pmol/(10(5)cells.15 min)] but no significant change in the apparent affinity (Km = 0.42 +/- 0.07 mumol/l). This inhibition of [3H]noradrenaline accumulation was distinct from that produced by the vesicular transport inhibitor reserpine. Pertussis toxin inhibition probably did not arise through an indirect action on the Na(+)-gradient because while, as expected, Na+,K(+)-ATPase inhibition reduced [3H]noradrenaline accumulation, pertussis toxin pretreatment always caused a further significant reduction even in the presence of maximally effective concentrations of ouabain. Stimulation of the cAMP-protein kinase A system by forskolin or 8-bromocyclic AMP also caused a reduction in [3H] noradrenaline accumulation but again pertussis toxin pretreatment always resulted in a further reduction. Thus, the data provide evidence for a pertussis toxin-sensitive element in the catecholamine accumulation process and are consistent with an action at a site directly associated with the transporter itself rather than with an indirect action via secondary processes.
Bunn
S J
SJ
Neuroscience Group, Faculty of Medicine, University of Newcastle, New South Wales, Australia.
O'Brien
K J
KJ
Boyd
T L
TL
Powis
D A
DA
D000313:Adrenal Medulla / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002838:Chromaffin System / Q000187:drug effects / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D046508:Culture Techniques; D000242:Cyclic AMP / Q000494:pharmacology; D003891:Desipramine / Q000494:pharmacology; D004347:Drug Interactions; D009638:Norepinephrine / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D037342:Pertussis Toxin; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D010566:Virulence Factors, Bordetella; D005576:Colforsin; D010042:Ouabain; D000242:Cyclic AMP; D037342:Pertussis Toxin; D003891:Desipramine; D009638:Norepinephrine