Capacitative Ca2+ influx and a Ca2+-dependent nonselective cation pathway are discriminated by genistein in mouse pancreatic acinar cells.
We have investigated the effect of genistein on the hormone-stimulated Ca2+ influx and on a 28pS nonselective cation channel in mouse pancreatic acinar cells using the Ca2+ indicator fluo3 and the patch-clamp technique. The identity of the Ca2+ influx pathway has not been established in this cell type so far. Therefore we have investigated the Ca2+-dependent nonselective cation channel as a potential pathway for Ca2+ influx. Capacitative Ca2+ entry was induced by depletion of intracellular Ca2+ stores with 500nM acetylcholine or with the Ca2+ ATPase inhibitor 2,5di-tert- butylhydroquinone. In the presence of 100microM genistein, Ca2+ release was unimpaired, whereas Ca2+ influx was reversibly suppressed. Patch-clamp experiments demonstrated that genistein had no effect on Ca2+-activated nonselective cation channels, the activity of which was measured in excised membrane patches (inside/out) or in the whole-cell configuration. Therefore we conclude that this 28pS nonselective cation channel does not contribute to Ca2+ influx into mouse exocrine pancreatic cells. With the exception of genistein and tyrphostin 25, other tyrosine kinase inhibitors such as methyl-2,5-dihydroxycinnamate, lavendustin A, herbimycin A, and tyrphostin B56 were without effect on Ca2+ signalling. Thus, the involvement of tyrosine phosphorylation in the activation of the Ca2+ entry mechanism in mouse pancreatic acinar cells is unclear.
Pfeiffer
F
F
2. Physiologisches Institut, Universität des Saarlandes, D-66421 Homburg/Saar, Germany.
Schmid
A
A
Schulz
I
I
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002412:Cations / Q000378:metabolism*; D002478:Cells, Cultured; D004553:Electric Conductivity; D019833:Genistein; D006728:Hormones / Q000502:physiology; D007425:Intracellular Membranes / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology; D007529:Isoflavones / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D010179:Pancreas / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D015398:Signal Transduction
D002412:Cations; D006728:Hormones; D007473:Ion Channels; D007529:Isoflavones; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D002118:Calcium