Effects of an inhibitor of myosin light chain kinase on amylase secretion from rat pancreatic acini.
Ca(2+)/calmodulin-dependent protein (CaM) kinases play an important role in Ca(2+)-mediated secretory mechanisms. Previously, we demonstrated that a CaM kinase II inhibitor KN-62 had a small inhibitory effect on amylase secretion stimulated by CCK. In the present study, we investigated the effects of a myosin light chain kinase (MLCK) inhibitor on amylase secretion and Ca(2+) signaling in rat pancreatic acini. A specific inhibitor of MLCK, wortmannin, inhibited amylase secretion stimulated by CCK-8 (30 pM) in a concentration-dependent manner. Wortmannin (10 microM) had no effects on basal secretion but reduced amylase secretion stimulated by CCK-8 (30 pM) by 67 +/- 3%. Wortmannin inhibited amylase secretion stimulated by calcium ionophore (A23187) and phorbol ester (TPA). Wortmannin also inhibited amylase response to thapsigargin by 76 +/- 8% and to both thapsigargin and TPA by 52 +/- 10%. Ca(2+) oscillations evoked by CCK-8 (10 pM) were inhibited by wortmannin (10 microM). Wortmannin had a little inhibitory effect on an initial rise in [Ca(2+)](i), and abolished a subsequent sustained elevation of [Ca(2+)](i) evoked by 1 nM CCK-8. In conclusion, MLCK plays a crucial role in amylase secretion from pancreatic acini and regulates Ca(2+) entry from the extracellular space.
Mizuno
N
N
Department of Internal Medicine II, Nagoya University School of Medicine, Nagoya, 466-8560, Japan.
Naruse
S
S
Kitagawa
M
M
Ishiguro
H
H
Hayakawa
T
T
D000681:Amylases / Q000378:metabolism*; D000730:Androstadienes / Q000494:pharmacology*; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors*; D010179:Pancreas / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D012844:Sincalide / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D000077191:Wortmannin
D000730:Androstadienes; D004791:Enzyme Inhibitors; D000001:Calcimycin; D019284:Thapsigargin; D009219:Myosin-Light-Chain Kinase; D000681:Amylases; D012844:Sincalide; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; D000077191:Wortmannin