title: Temperature-dependent alteration of insulin by plasma or serum from rats with N-methylacetamide-induced diabetes.
abstract: Insulin is degraded in plasma or serum from NMMAA-diabetic rats, at 37 degrees C in vitro, as shown by losses of both immunoreactivity and biological activity on fat pad tissue. The rate of insulin degradation was not notably influenced by plasma pH, in the range 7.2-8.3. Presumably due to destruction of insulin in the course of the 120 min bioassay incubation at 37 degrees C and pH 7.4, the potency of crystalline insulin on fat pad tissue was apparently lower in the presence of serum from NMMAA-poisoned rats than with control serum. Although plasma from control rats also lost some insulin within 120 min at 37 degrees C, the loss was much less pronounced. At 0 degree C, no loss of insulin occurred in serum samples from the poisoned animals. Therefore, the radioimmunoassay, which is performed at 0 degree C, yields valid measurements of insulin concentrations in these samples. Our observations provide an explanation for the erroneously low values of insulin detected by bioassay in serum from NMMAA-diabetic rats.
mesh_terms: D000081:Acetamides / Q000494:pharmacology*; D000273:Adipose Tissue / Q000187:drug effects; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000097:blood* / Q000139:chemically induced; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000097:blood*; D011863:Radioimmunoassay; D051381:Rats; D013696:Temperature; D013997:Time Factors
chemical_list: D000081:Acetamides; D001786:Blood Glucose; D007328:Insulin; C018595:N-methylacetamide