Mutually Distinctive Gradients of Three Types of Intestinal Alkaline Phosphatase along the Longitudinal Axis of the Rat Intestine

Abstract

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.

Intestinal alkaline phosphatase: multiple biological roles in maintenance of intestinal homeostasis and modulation by diet

“…This information is required to more clearly delineate the respective roles of IAP and other AP isoforms. Combining chromatography, electrophoresis, enzymology, and immunochemistry will help resolve this complexity 102–104 …”

In Vitro Intestinal and Liver Models for Toxicity Testing

“…The small intestine is divided into three sections: duodenum, jejunum, and ileum . Both the small and large intestines exhibit different properties across the length of the organ. ,,, …”

“…26 Both the small and large intestines exhibit different properties across the length of the organ. 6,22,27,28 Radially, the GI tract has 4 distinct tissue layers: mucosa, submucosa, muscularis externa, and serosa/adventitia. 26 The mucosa is the innermost layer, exposed to the intestinal luminal contents and is the most important layer of the intestine for absorptive and secretory functions.…”