Arachidonic acid is functioning as a second messenger in activating the Ca2+ entry process on H1-histaminoceptor stimulation in DDT1 MF-2 cells.
This study was carried out to identify the cellular component activating the histamine-stimulated Ca2+ entry in vas-deferens-derived DDT1 MF-2 cells. H1-histaminoceptor stimulation resulted in a rise in intracellular Ca2+ concentration, caused by Ca2+ release from inositol phosphate-sensitive Ca2+ stores and Ca2+ entry from the extracellular space, accompanied by a transient Ca(2+)-activated outward K+ current. The histamine-evoked K+ current was still observed after preventing inositol phosphate-induced Ca2+ mobilization by intracellularly applied heparin. This current was activated by Ca2+ entry from the extracellular space, because it was abolished in the presence of the Ca(2+)-channel blocker La3+ or under Ca(2+)-free conditions. H1-histaminoceptor-activated Ca2+ entry was also observed in the presence of intracellularly applied Ins(1,4,5)P3 and Ins(1,3,4,5)P4, depleting their respective Ca2+ stores and pre-activating the inositol phosphate-regulated Ca2+ entry. Thus the ability of histamine to activate Ca2+ entry independently of Ca2+ mobilization and the formation of inositol phosphates suggests that another component is involved to initiate the Ca(2+)-entry process. It was observed that H1-histaminoceptor stimulation resulted in a pronounced release of arachidonic acid (AA) in DDT1 MF-2 cells. Exogenously applied AA induced a concentration-dependent increase in internal Ca2+ due to activation of Ca2+ entry from the extracellular space. Slow inactivation of the AA-sensitive Ca2+ channels is suggested by the slow decline in Ca2+ entry. In accord, the histamine-induced Ca2+ entry was not observed with AA-pre-activated Ca2+ channels. Inhibition of the lipoxygenase and cyclo-oxygenase pathway did not affect the AA-induced Ca2+ and the concomitant K+ current were decreased in the presence of AA and caused by Ca2+ mobilization from internal stores. Blocking this internal Ca2+ release by heparin, in the presence of AA, resulted in abolition of the histamine-induced Ca(2+)-regulated K+ current. These observations show that AA, released on H1-histaminoceptor stimulation in DDT1 MF-2 cells, is functioning as a second messenger to activate plasma-membrane Ca2+ channels promoting Ca2+ entry from the extracellular space.
Groningen Institute for Drug Studies, Department of Pharmacology/Clinical Pharmacology, Faculty of Medicine, University of Groningen, The Netherlands.
L
L
van der Zee
A
A
Nelemans
A
A
den Hertog
D016718:Arachidonic Acid / Q000494:pharmacology / Q000502:physiology*; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002460:Cell Line; D006632:Histamine / Q000494:pharmacology; D007295:Inositol Phosphates / Q000494:pharmacology; D007700:Kinetics; D009130:Muscle, Smooth / Q000378:metabolism*; D015221:Potassium Channels / Q000502:physiology; D011969:Receptors, Histamine H1 / Q000502:physiology*; D015290:Second Messenger Systems
D007295:Inositol Phosphates; D015221:Potassium Channels; D011969:Receptors, Histamine H1; D016718:Arachidonic Acid; D006632:Histamine; D002118:Calcium