Altered intestinal and renal brush border amino-oligopeptidase structure in diabetes and metabolic acidosis: normal and biobreed (BB) rats.
Amino-oligopeptidase (AOP, aminopeptidase N), a major glycoprotein hydrolase in intestinal and kidney brush border membranes, plays a crucial role in digesting peptide nutrients and salvaging filtered peptides. The molecular structure of rat intestinal and kidney AOP was compared for normal Wistar and congenitally diabetic BB Wistar (BBd) rats. Brush border membranes were isolated, solubilized with Triton X-100, and the AOP specifically immunoprecipitated with polyvalent rabbit antiserum and analyzed on 7% sodium dodecyl sulfate (SDS)-acrylamide electrophoresis. While the specific hydrolytic activity was maintained, BBd rats displayed an altered migration of AOP on SDS gels. Intestinal AOP migrated as a smaller species (130 kd) in the BBd than in the normal Wistar (135 to 140 kd). In some BBd rats, additional intestinal AOP species were observed (a 130- to 135-kd doublet or a 125-, 130-, or 135-kd triplet). Kidney AOP migrated as a broader band (125 to 140 kd) than intestine for all rat groups, probably due to carbohydrate chain heterogeneity, and was approximately 5 kd smaller in the BBd rat than in the normal Wistar. In contrast, no mass change was found in diabetes induced by streptozotocin (STZ). The altered intestinal AOP in the BBd rat was present when first inserted into the brush border membrane (6 hours after intraperitoneal [35S]methionine labeling), and hence was not due to nonenzymatic glycosylation (NEG). Abnormal intestinal and kidney AOP structure appeared in early diabetes, irrespective of high plasma glucose levels or ketoacidosis, and was reversed following evolution of the diabetes under prolonged (21 to 120 days) insulin treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Najjar
S M
SM
Department of Medicine, Stanford University School of Medicine, CA 94305.
Hampp
L T
LT
Rabkin
R
R
Gray
G M
GM
D000138:Acidosis / Q000378:metabolism*; D000626:Aminopeptidases / Q000032:analysis* / Q000737:chemistry; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D018826:CD13 Antigens; D002241:Carbohydrates / Q000737:chemistry; D003920:Diabetes Mellitus / Q000201:enzymology*; D004586:Electrophoresis; D007328:Insulin / Q000494:pharmacology; D007422:Intestines / Q000201:enzymology*; D007668:Kidney / Q000201:enzymology*; D008871:Microvilli / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains
D001786:Blood Glucose; D002241:Carbohydrates; D007328:Insulin; D000626:Aminopeptidases; D018826:CD13 Antigens