Inositol 1,3,4,5-tetrakisphosphate and inositol 1,4,5-trisphosphate act by different mechanisms when controlling Ca2+ in mouse lacrimal acinar cells.
In internally perfused single lacrimal acinar cells the competitive inositol 1,4,5-trisphosphate (Ins 1,4,5-P3)-antagonist heparin inhibits the ACh-evoked K+ current response mediated by internal Ca2+ and also blocks both the Ins 1,4,5-P3-evoked transient as well as the sustained K+ current increase evoked by combined stimulation with internal Ins 1,4,5-P3 and inositol 1,3,4,5-tetrakisphosphate (Ins 1,3,4,5-P4). When, during sustained stimulation with both Ins 1,4,5-P3 and Ins 1,3,4,5-P4, one of the inositol polyphosphates is removed, the K+ current declines; whereas removal of Ins 1,4,5-P3 results in an immediate termination of the response, removal of Ins 1,3,4,5-P4 only causes a very gradual and slow reduction in the current. Ins 1,3,4,5-P4 is therefore not an acute controller of Ca2+ release from stores into the cytosol, but modulates the release of Ca2+ induced by Ins 1,4,5,P3 by an unknown mechanism, perhaps by linking Ins 1,4,5 P3-sensitive and insensitive Ca2+ stores.
Changya
L
L
MRC Secretory Control Research Group, University of Liverpool, England.
Gallacher
D V
DV
Irvine
R F
RF
Petersen
O H
OH
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006493:Heparin / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D007765:Lacrimal Apparatus / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D015221:Potassium Channels / Q000502:physiology; D013403:Sugar Phosphates / Q000494:pharmacology*
D007295:Inositol Phosphates; D015221:Potassium Channels; D013403:Sugar Phosphates; C081655:inositol-1,3,4,5-tetrakisphosphate; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D000109:Acetylcholine; D002118:Calcium