Evidence for a compensatory increase in synthesis of brush border enzymes in the jejunum of Irish Setters with gluten-sensitive enteropathy
Manners, H.K.; Sørensen, S.H.; Embaye, H.; Odedra, R.M.; Batt, R.M.
American Journal of Veterinary Research 59(11): 1392-1397
1998
ISSN/ISBN: 0002-9645 PMID: 9829395 Document Number: 494733
Biosynthesis of aminopeptidase N (ApN), alkaline phosphatase (AP) and total microvillus membrane protein was studied in a litter of 6 Irish Setters with gluten-sensitive enteropathy (GSE) and 3 healthy Greyhounds. Explants obtained from affected dogs at 4 and 12 months were maintained in vitro and were compared with material from healthy dogs. Biosynthesis of ApN and AP was monitored by incorporation of [35S]methionine and immunoprecipitation of these enzymes. Jejunal explants from affected Irish Setters had significantly higher rates of biosynthesis of total protein, microvillus membrane protein, AP and ApN compared with control tissue. Two forms of ApN with apparent molecular mass of 155 and 135 kDa and 4 forms of AP with apparent molecular mass of 210 to 260, 150, 130, and 105 kDa were identified in total membrane fractions from control and affected dogs. It is suggested that reduced activities of ApN and AP in dogs with GSE are not attributable to decreased synthesis of these proteins and that enhanced synthesis of microvillar membrane proteins may be a compensatory response to enterocyte damage. The 150-kDa form of AP was most prominent in tissue from the most affected dogs, probably representing an early form of this enzyme.