Background/Aims: A descending gradient of alkaline phosphatase (AP) activity is well known to exist in the rat intestine. To understand the physiological role(s) of intestinal AP (IAP), we examined in detail the distribution of IAP subtypes along the longitudinal axis of the rat intestine. Methods: The consecutive 2-cm segments of the upper intestine were analyzed by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) followed by staining for IAP activity. The reverse transcription-polymerase chain reaction was conducted to assess the relative levels of tissue mRNA for the 2 distinct genes of rat IAP, rIAP-I and rIAP-II. Results: A descending gradient of IAP activity was found along the upper small intestine, where 3 bands of the activity, termed types 1, 2 and 3 from the anode were located on SDS-PAGE gels. Along the longitudinal axis, types 1 and 3 showed ascending and descending gradients, respectively; whereas type 2 had a broad uniform distribution. The mRNA level for rIAP-I showed an ascending distribution, and that of rIAP-II, a descending one. Type 3 IAP was drastically diminished in duodenum of cysteamine-ulcer rats, but type 1 remained constant. Conclusion: These distinctive gradients of IAP subtypes may provide a clue to scrutinize the physiological significance of AP in the rat intestine, which is a flow system with polarity.
SummaryDuodenal alkaline phosphatase activities were measured in rats treated with cysteamine, a drug which causes duodenal ulcers in experimental animals. In the proximal duodenum, a significant decrease in alkaline phosphatase was observed 24 h after cysteamine injection. The inhibitory effect seems site-specific, since the enzyme in the upper jejunum remained unchanged. Moreover, the effect of cysteamine is apparently alkaline phosphatase-specific, because duodenal acid phosphatase, leucine aminopeptidase, and bicarbonate-dependent ATPase did not show any significant change in activity. A mechanism of the inhibitory effect of cysteamine on alkaline phosphatase is discussed.
SummaryEffect of a restricted 2-h daily feeding period on the ulcerogenicity of cysteamine was studied in rats with special reference to duodenal alkaline phosphatase activity.
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