Salivary gland glucagon is a fictitious substance due to tracer-degrading activity resistant to protease inhibitors.
A high level of glucagon immunoreactivity was apparently detected in acid-saline extract from rat submandibular glands, but tracer glucagon added to the assay mixture was mostly damaged in spite of the presence of protease inhibitors commonly used in radioimmunoassay. Gel-filtration of the extract on a Bio-Gel P-10 column revealed strong tracer-degrading activity at the void fraction where the apparent immunoreactivity was eluted. Serial changes in apparent immunoreactivity of the extract fit well on the theoretical curve of an exponential tracer degradation. These findings indicate that the salivary gland glucagon is a fictitious substance due to tracer degradation during radioimmunoassay. Further study revealed that the glucagon molecule was hydrolyzed at the arginyl bonds and split into two fragments during incubation with the acid-saline extract from rat submandibular glands.
D000818:Animals; D002850:Chromatography, Gel; D004492:Edetic Acid; D005189:False Positive Reactions; D005934:Glucagon / Q000032:analysis*; D006868:Hydrolysis; D008297:Male; D008722:Methods; D051381:Rats; D011919:Rats, Inbred Strains; D013363:Submandibular Gland / Q000032:analysis*
D005934:Glucagon; D004492:Edetic Acid