Background: Upregulation of cobalamin receptor expression has been described in the ileum of hypocobalaminemic dogs with chronic inflammatory enteropathy (CIE). However, expression in the jejunum, another potential site of cobalamin absorption, has not been evaluated.
Objectives: To evaluate mRNA and protein expression of cobalamin receptors in the jejunum and ileum of control dogs and dogs with CIE. Animals: Client-owned dogs: 15 control dogs and 32 dogs with CIE.
Methods: Retrospective cross-sectional study. mRNA and protein expression of two cobalamin receptor subunits (AMN and CUBN) were evaluated using RNA in situ hybridization and immunohistochemistry, respectively, in formalin-fixed paraffin embedded tissues from the jejunum and ileum. Expression levels were compared between control dogs and dogs with CIE.
Results: mRNA and protein expression of both subunits were detected in the jejunum and ileum of all control dogs and dogs with CIE. No significant differences in mRNA expression were identified between groups. In the jejunum, AMN protein expressions did not differ, while CUBN protein expression was significantly increased in both villi (P = .0006, mean difference of immunopositive area [95% CI]: 21,822µm2 [7,049-36,595µm2]) and crypts (P = .0005, 26,170µm2 [13,543-38,496µm2]) of dogs with CIE. In the ileum, protein expression of both subunits was not significantly different in the villi but was significantly increased in the crypts (AMN: P = .0108, 40,275µm2 [9,946-70,605µm2]; CUBN: P = .0280, 22,037µm2 [2,532-41,541µm2]) of dogs with CIE. Conclusions and clinical importance: In addition to the ileum, the jejunum may contribute to cobalamin absorption.
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