ABSTRACT
IgA is the predominant immunoglobulin class in mucosal secretions and secretory deficiencies may predispose to chronic enteropathies. The polymeric immunoglobulin receptor (pIgR) facilitates the transport of IgA across the epithelial border. Critical to the transport of IgA by pIgR is the presence of a polypeptide joining chain (J-chain) linking the IgA monomers of the dimeric IgA molecule. In this study we examine the difference in expression of mRNA transcripts for pIgR, alpha-chain and J-chain by real-time reverse-transcription polymerase chain reaction (RT-PCR) in endoscopic biopsies from the duodenum of dogs with and without chronic diarrhoea. One-step, real-time RT-PCR was used to quantify the level of expression of transcripts for the housekeeper gene G3PDH, pIgR, alpha-chain and J-chain. There was no significant difference in expression of any transcript between dogs with (n=11) and without (n=8) chronic diarrhoea. Expression of alpha-chain mRNA in both groups had a similar bimodal distribution, as individuals either expressed relatively 'high' or 'low' levels of this transcript. The secretion of IgA by plasma cells is under the control of Th-2 cytokines, therefore the finding of 'high' and 'low' levels of alpha-chain expression may reflect different levels of these cytokines in duodenal mucosa.
Subject(s)
Immunoglobulin J-Chains/genetics , Immunoglobulin alpha-Chains/genetics , RNA, Messenger/analysis , RNA, Messenger/genetics , Receptors, Polymeric Immunoglobulin/genetics , Reverse Transcriptase Polymerase Chain Reaction/methods , Animals , Base Sequence , DNA Primers/genetics , Diarrhea/genetics , Diarrhea/immunology , Diarrhea/veterinary , Dog Diseases/genetics , Dog Diseases/immunology , Dogs , Duodenum/immunology , Female , Intestinal Mucosa/immunology , Male , Reproducibility of Results , Reverse Transcriptase Polymerase Chain Reaction/statistics & numerical dataABSTRACT
OBJECTIVE: To determine relationships between fecal consistency and colonic microstructure and absorptive function in dogs with and without nonspecific dietary sensitivity. ANIMALS: 12 dogs with nonspecific dietary sensitivity (affected) and 9 healthy dogs (controls). PROCEDURE: Affected dogs were fed 4 test diets and control dogs, 3 diets for 4 weeks each in a crossover design. Fecal consistency was assessed daily. At the end of each feeding period, electrolyte and water transport were assessed, and colonic biopsy specimens were obtained for histologic examination and measurement of crypt water uptake by use of confocal microscopy. RESULTS: Feces were consistently looser in affected dogs. In control dogs, we detected net colonic absorption of sodium and chloride and secretion of potassium and bicarbonate. Absorption of sodium and chloride was less in affected dogs, compared with controls, indicating that electrolyte transport was disrupted in affected dogs. This disruption was accentuated during feeding of diets associated with significantly poorer fecal consistency (ie, loose feces). Fecal consistency was inversely correlated with crypt water absorption, which was reduced in affected dogs. Colonic crypts were shorter and less dense in affected dogs fed diets associated with poor fecal consistency, compared with affected dogs fed other diets or with control dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Colonic transport function is a major determinant of fecal consistency in dogs. Dogs with nonspecific dietary sensitivity are particularly susceptible to diet-induced changes in absorptive function. Such changes are associated with damage to colonic microstructure, disrupted electrolyte transport, and failure to dehydrate luminal contents.
Subject(s)
Colon/metabolism , Colonic Diseases/metabolism , Dog Diseases/metabolism , Feces , Food Hypersensitivity/metabolism , Animal Feed , Animals , Biopsy/veterinary , Colon/pathology , Colonic Diseases/pathology , Cross-Over Studies , Dog Diseases/pathology , Dogs , Electrolytes/analysis , Feces/cytology , Food Hypersensitivity/pathology , Intestinal Absorption/physiology , Intestinal Mucosa/cytology , Intestinal Mucosa/metabolism , Intestinal Mucosa/pathologyABSTRACT
Cats have a requirement for dietary protein two to three times that of omnivores and herbivores. This was reported to be due to the hepatic catabolic enzymes of this species being set to a permanently high level and, therefore, showing little adaptation to low dietary protein. A major mechanism for adapting to dietary protein in other species is amino acid oxidation (hereafter referred to as protein oxidation), and the objective of this study was to determine whether protein oxidation in cats was correlated with protein intake. Net protein and net fat oxidation in six adult cats were studied directly from gas exchanges using indirect calorimetry, after feeding moderate protein (MP; 35% energy) and high protein (HP; 52% energy) diets. Protein oxidation was significantly higher (P < 0.05) when cats were fed the HP diet (28.4 plus minus 0.7 mg/min) rather than the MP diet (20.4 plus minus 0.8 mg/min). Fat oxidation was significantly higher (P < 0.05) when cats consumed the MP diet (9.0 plus minus 0.7 mg/min) rather than the HP diet (4.7 plus minus 0.5 mg/min). Protein oxidation was significantly correlated (linear regression, R(2) = 46.0, P < 0.05) with protein intake such that the mean ratio of 18-h oxidation: 18-h intake was 1.2 on both diets. Fat oxidation was significantly correlated (linear regression, R(2) = 18.9, P < 0.05) with fat intake such that the mean ratio of 18-h fat oxidation: 18-h fat intake was 1.1 (MP) and 0.9 (HP). This study demonstrated that cats adapt net protein oxidation at these levels of protein intake, and the reason for the high dietary protein requirement of this species is, therefore, unclear.