Changes in intestinal alkaline phosphatase activity in cholera toxin-treated rats.

Miura, Soichiro; Asakura, Hitoshi; Morishita, Tetsuo; Hibi, T.; Munakata, Y; Kobayashi, Kensuke; Tsuchiya, Masaharu

doi:10.1136/gut.23.6.507

Cited by 14 publications

(3 citation statements)

References 19 publications

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“…Alkaline phosphatase is present in the brush border of enterocytes and its activity has been exploited as a marker to confirm microvilli function and potential disruption of the microvilli layer (Fan et al 1999 ; Miura et al 1982 ). ALP activity was assessed after 48 h of exposure to 50 µg/ml SAS by measuring the turnover of p-nitrophenylphosphate to p-nitrophenol by alkaline phosphatase.…”

Section: Resultsmentioning

confidence: 99%

Investigating the effects of differently produced synthetic amorphous silica (E 551) on the integrity and functionality of the human intestinal barrier using an advanced in vitro co-culture model

et al. 2020

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E 551, also known as synthetic amorphous silica (SAS), is the second most produced food additive. However, according to the re-evaluation of E 551 by the European Food Safety Authority (EFSA) in 2018, the amount of available data on the oral toxicity of food grade E 551 is still insufficient for reliable risk assessment. To close this gap, this study aimed to investigate six food-grade SAS with distinct physicochemical properties on their interaction with the intestinal barrier using advanced in vitro intestinal co-cultures and to identify potential structure–activity relationships. A mucus-secreting Caco-2/HT-29/Raji co-culture model was treated with up to 50 µg/ml SAS for 48 h, which represents a dose range relevant to dietary exposure. No effects on cell viability, barrier integrity, microvilli function or the release of inflammatory cytokine were detected after acute exposure. Slight biological responses were observed for few SAS materials on iron uptake and gene expression levels of mucin 1 and G-protein coupled receptor 120 (GPR120). There was no clear correlation between SAS properties (single or combined) and the observed biological responses. Overall, this study provides novel insights into the short-term impact of food-relevant SAS with distinct characteristics on the intestinal epithelium including a range of intestine-specific functional endpoints. In addition, it highlights the importance of using advanced intestinal co-cultures embracing relevant cell types as well as a protective mucus barrier to achieve a comprehensive understanding of the biological response of food additives at the intestinal barrier in vitro.

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Section: Resultsmentioning

confidence: 99%

Investigating the effects of differently produced synthetic amorphous silica (E 551) on the integrity and functionality of the human intestinal barrier using an advanced in vitro co-culture model

et al. 2020

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“…The reason why only alkaline phosphatase activity in intestinal lymph was selectively enhanced after toxin exposure is uncertain. A previous study from our laboratory, however, sug gested that the changes in alkaline phospha tase activity in intestinal lymph by cholera toxin might be mediated through activation of the adenylate cyclase-cAMP system [29], Due to the administration of somatosta tin, the increase in alkaline phosphatase, aminopeptidase and sucrase activity in the intestinal lumen and alkaline phosphatase activity in the intestinal lymph caused by cholera toxin administration were markedly inhibited. From these observations, it is in dicated that somatostatin inhibits cholera toxin-induced hypersecretion in water and enzyme activities by affecting this event beyond the formation of cAMP.…”

Section: Discussionmentioning

confidence: 99%

Inhibitory Effect of Somatostatin on Cholera Toxin-Induced Diarrhea and Glycoenzyme Secretion in Rat Intestine

Yoshioka¹,

Asakura²,

Hamada³

et al. 1987

Digestion

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The effects of somatostatin on cholera toxin-induced secretory diarrhea and the appearance of glycoenzymes in the intestinal lumen and intestinal lymph were investigated in rat small intestine. After exposure to cholera toxin, marked fluid accumulation in the small intestinal tract and elevation of the jejunal mucosal cyclic AMP (cAMP) concentration were observed. The activity of alkaline phosphatase, aminopeptidase and sucrase increased in the intestinal lumen after toxin exposure. In intestinal lymph, alkaline phosphatase activity was increased after cholera toxin administration, while aminopeptidase activity remained unchanged. Somatostatin suppressed cholera toxin-induced secretory diarrhea, but it did not affect the elevated mucosal cAMP concentration. This peptide also inhibited the appearance of glycoenzymes in the intestinal lumen and lymph induced by cholera toxin administration. These results suggest that somatostatin exerts its inhibitory effects on cholera toxin-induced secretory diarrhea and on the appearance of glycoenzymes in the intestinal lumen and lymph by affecting processes beyond cAMP formation.

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“…The inhibitory action of timolol on the activity of adenylate cyclase in the iris-ciliary body, the tissue responsible for aqueous humour secretion, bears a close resemblance to the inhibitory effect of chlorpromazine on the activity of adenylate cyclase in intestinal epithelial cell membranes, which also deal with active secretion of water or hypersecretion as in cholera cases (Holmgren et al 1978;Miura et al 1982). As chlorpromazine is also an -S-containing compound and an inhibitor of adenylate cyclase (Wolf 8c Jones 1970), the role of sulphur-containing heterocyclic compounds in controlling abnormal transport of ions or hypersecretion of water across membranes is of paramount importance.…”

Section: +24% Nonementioning

confidence: 99%

Timolol inhibits adenylate cyclase activity in the iris‐ciliary body and trabecular meshwork of the eye and blocks activation of the enzyme by salbutamol

Phylactos

1986

Acta Ophthalmologica

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The enzymatic activity of adenylate cyclase in homogenates and membrane-rich fractions prepared from rabbit iris-ciliary bodies and bovine trabecular meshwork was found to be inhibited by timolol. Treatment of iris-ciliary body homogenates with Triton X-305 resulted in abolition of the inhibitory effect of the drug on the activity of the enzyme. The stimulatory effect of salbutamol on the enzyme was also susceptible to blockade by timolol. It is suggested that the hypotensive action of timolol on intraocular pressure results from structural and functional changes induced on the plasma membranes of the iris-ciliary body and trabecular meshwork by the thiadiazole group of the molecule, and, also, from the occupation of the adrenergic receptors of the iris-ciliary body by the tert-butylamino-2-hydroxypropoxy part of the compound.

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Changes in intestinal alkaline phosphatase activity in cholera toxin-treated rats.

Cited by 14 publications

References 19 publications

Investigating the effects of differently produced synthetic amorphous silica (E 551) on the integrity and functionality of the human intestinal barrier using an advanced in vitro co-culture model

Investigating the effects of differently produced synthetic amorphous silica (E 551) on the integrity and functionality of the human intestinal barrier using an advanced in vitro co-culture model

Inhibitory Effect of Somatostatin on Cholera Toxin-Induced Diarrhea and Glycoenzyme Secretion in Rat Intestine

Timolol inhibits adenylate cyclase activity in the iris‐ciliary body and trabecular meshwork of the eye and blocks activation of the enzyme by salbutamol

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