High-molecular IRI (big, big insulin) in islet cell adenoma.
In agreement with data previously reported (Yalow and Berson 1973), after gel filtration of acid-ethanol extracts of islet cell adenomas (performed in 3 M acetic acid) 1.4% to 1.8% of total immunoreactive insulin (IRI) eluted ahead of proinsulin. The high-molecular IRI (HM-IRI) was, however, found to be heterogenous in size and consisted of at least three components, the major one having an estimated molecular weight of about 50,000. Under certain conditions, HM-IRI was partially dissociated into proinsulin- and insulin-like components. We conclude that HM-IRI does not represent a precursor of proinsulin and insulin, but probably a self-association product of the peptides or an association of insulin and proinsulin to other proteins extracted from tumor tissue.
D000236:Adenoma / Q000378:metabolism*; D007516:Adenoma, Islet Cell / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000276:immunology / Q000378:metabolism*; D008970:Molecular Weight; D011384:Proinsulin; D011863:Radioimmunoassay
D007328:Insulin; D011384:Proinsulin