PubMed · 8753469
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T Hayakawa, S Naruse, M Kitagawa, T Kondo. 1995. [Macroamylase].. https://pubmed.ncbi.nlm.nih.gov/8753469/
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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.
A few common spices or their active principles were examined for their possible influence on digestive enzymes of pancreas in experimental rat. Groups of animals were maintained for 8 weeks on the following spice diets: curcumin (0.5%), capsaicin (15 mg%), piperine (20 mg%), ginger (50 mg%), cumin (1.25%), fenugreek (2%), mustard (250 mg%) and asafoetida (250 mg%). Dietary curcumin, capsaicin, piperine, ginger, fenugreek and asafoetida prominently enhanced pancreatic lipase activity. Curcumin, capsaicin, piperine, ginger, cumin and asafoetida also stimulated pancreatic amylase. Trypsin was significantly stimulated by curcumin, capsaicin, piperine, ginger and cumin, while chymotrypsin was stimulated by all the spices tested except mustard. This stimulatory influence of test spices on the pancreatic digestive enzymes was however not observed when their intake was restricted to a single oral dose. The positive influences on the pancreatic digestive enzymes exerted by a good number of spices consumed in diet could be a factor contributing to the well recognised digestive stimulant action of spices.
Caffeine has been found to inhibit the formation and action of Ca2+-mobilizing inositol 1,4,5-trisphosphate (IP3) in pancreatic acinar cells. The aim of the present study was to investigate the effects of caffeine on cytoplasmic Ca2+ concentrations ([Ca2+]i) and amylase release in response to different agonists. [Ca2+]i was determined by cytofluorometry using fura-2 as indicator and amylase release with a substrate reagent. Stimulation with low concentrations of carbachol or cholecystokinin octapeptide (CCK-8) induces [Ca2+]i oscillations whereas higher concentrations cause sustained elevation of [Ca2+]i. The less efficacious agonists pilocarpine and CCK-JMV-180 evoke oscillations only. Caffeine inhibited carbachol-induced elevation of [Ca2+]i and amylase responses in a competitive manner, abolishing the responses to low and incompletely inhibiting the responses to high concentrations of the agonist. Also, the [Ca2+]i elevations by pilocarpine were abolished by caffeine. The effects on CCK-8-induced elevation of [Ca2+]i and amylase secretion were paradoxical, the caffeine inhibition being more pronounced at high than at low concentrations of CCK-8. This enigma was further emphasized by moderate effects of caffeine on the responses to CCK-JMV-180. The results indicate that carbachol, pilocarpine and high concentrations of CCK-8 elicit IP3-mediated responses and that CCK-JMV-180 and low concentrations of CCK-8 elevate [Ca2+]i and stimulate amylase release by another signal transduction mechanism.