Genistein, a tyrosine kinase inhibitor, inhibited cholecystokinin (CCK)-induced maximal amylase release from rat pancreatic acini by 18, 31, and 46% at concentrations of 100, 300, and 750 microM, respectively, after 30 min preincubation. Genistein similarly decreased amylase release stimulated by bombesin but not that stimulated by secretin or vasoactive intestinal peptide. The steps of stimulus-s

CCK rapidly converted Ca2+/calmodulin kinase II (CaMK II) to a Ca(2+)-independent form with peak action at 30 sec followed by decline to the basal level at 10 min. The threshold concentration of CCK for this action was 30 pM and maximum effect occurred at 1 nM, which induced a 6-10-fold increase. Bombesin and carbachol similarly induced CaMK II autonomous activity, whereas secretin and JMV 180 did

The existence and activation of mitogen-activated protein (MAP) kinase in isolated pancreatic acini have been demonstrated. Immunoblotting and immunoprecipitation revealed two forms of MAP kinase in pancreatic acini, with relative molecular masses of approximately 42 and 44 kDa. Both forms of MAP kinase were activated by cholecystokinin (CCK). The threshold concentration of CCK was approximately 3

Cholecystokinin (CCK) has recently been shown to activate mitogen-activated protein (MAP) kinase in rat pancreatic acini [Duan and Williams, Am. J. Physiol. 267 (Gastrointest. Liver Physiol. 30): G401-G408, 1994]. To evaluate the mechanism of MAP kinase activation, we studied the effects of CCK on MAP kinase kinase (MEK) in rat pancreatic acini. Two forms of MEK were identified by immunoblotting,

Previous studies indicated that there was an alkaline sphingomyelinase (SMase) activity in small intestine, but its properties have not been studied in detail. In the present work, we studied the distribution of this enzyme activity in rat gastrointestinal tract and characterized it in intestinal mucosal homogenates. Little alkaline SMase activity was detected in the stomach and the duodenum. The

Cholecystokinin (CCK) is known to rapidly and transiently increase both [Ca2+]iand autonomous CaM kinase II activity in rat pancreatic acini. Because induction of autonomous activity may involve intramolecular autophosphorylation, the effects of protein phosphatase inhibitors were examined. None of the inhibitors tested (okadaic acid, calyculin A, and cyclosporin A) affected basal activity. Okadai

The hydrolysis of sphingomyelin has been found to generate important signals regulating cell proliferation, differentiation and apoptosis. However, the enzymes responsible for digestion of dietary sphingomyelin have not been well documented. This study demonstrates the occurrence of a sphingomyelinase (SMase) in both human hepatic bile and gallbladder bile. The enzyme was equally found in both bac

Escherichia coli express fimbriae-associated adhesins through which they attach to mucosal cells and activate a cytokine response. The receptors for E. coli P fimbriae are the globoseries of glycosphingolipids; Gal alpha 1-->4Gal beta-containing oligosaccharides bound to ceramide in the outer leaflet of the lipid bilayer. The receptors for type 1 fimbriae are mannosylated glycoproteins rather than

By attaching to cells or secreted mucosal components, microbes are thought to avoid elimination by the flow of secretions that constantly wash mucosal surfaces. The attached state enhances their ability to trap nutrients and allows the bacteria to multiply more efficiently than do unattached bacterial cells. Attachment is therefore regarded as an end result in itself, and emphasis has been placed

The hydrolysis of sphingomyelin (SM) generates important signals regulating cell proliferation and apoptosis. Acid and neutral sphingomyelinases (SMase) have been identified and their biological effects intensively studied. We recently found in human bile a novel alkaline SMase that may have important roles in hepatobiliary diseases. In this work, we purified the enzyme and studied the factors inf

Dietary sphingomyelin (SM) undergoes sequential cleavage to ceramide and sphingosine in the intestine. A distinctive intestinal sphingomyelinase (SMase) with alkaline pH-optimum was earlier identified by us. The activity was highest in middle and lower small intestine, but its role in SM digestion has not been clarified. In this study we examined the extension and capacity of SM digestion in vivo.

BACKGROUNDThere is a renewed interest in metabolism of sphingolipids because of their role in signal transduction. Sphingomyelin is the dominating phospholipid in human milk but its metabolism and possible function in the gastrointestinal tract of breast fed infants is unknown. We explored whether bile salt-stimulated milk lipase has a role in sphingolipid metabolism.METHODSIn vitro assays of sphi

Two studies were conducted to investigate the role of meat and arachidonic acid in colonie signal transduction, particularly protein kinase C (PKC) activation. In Study 1, 26 male Wistar rats were fed a casein‐ or a beef‐based diet for four weeks. PKC activity was measured from the proximal and distal colonie mucosa and diacylglycerol concentration from fecal samples. The beef diet significantly i

Uropathogenic Escherichia coli attach to epithelial cells through P fimbriae that bind Galα1‐4Galβ‐oligosaccharide sequences in cell surface glycosphingolipids. The binding of P‐fimbriated E. coli to uroepithelial cells causes the release of ceramide, activation of the ceramide signalling pathway and a cytokine response in the epithelial cells. The present study examined the molecular source of ce

Previous studies showed that bile salts had apromoting effect on colon cancer development and thiseffect was inhibited by ursodeoxycholate (UDC). Werecently found that both human colorectal adenomas and carcinomas were associated with a specificdecrease in alkaline sphingomyelinase activity. In thiswork, we compared the effects of ursodeoxycholate andother bile salts on the levels of rat intestina