title: Insulin release in vitro from islet tissues and adenomas of rats treated with nicotinamide and streptozotocin. The effects of glucose.
abstract: Young male Holtzman rats injected with nicotinamide and streptozotocin develop grossly visible tumors of pancreatic islet tissue. Using an i.v. glucose tolerance test, some tumor-bearing animals exhibited a vigorous (or fast) response to glucose loading (Diabetic Index = 0.47), whereas others showed a subdiabetic (or slow) response (Diabetic Index = 2.34). In vitro perifusion studies demonstrate that tumor pieces from both groups of rats released immunoreactive insulin (IRI) in response to glucose; tumors from fast responding rats showed a rapid monophasic release of IRI (i.e., rapid transient release with little secondary phase), while tumors from slow responders released IRI in a biphasic pattern resembling that of normal islets. A population of large islet masses (or microscopic tumors), isolated from drug-treated rats by collagenase digestion of the pancreas of tumor-containing rats, exhibited glucose-stimulated IRI release that resembled the pattern of the tumor from the same animal. Isolated islets of Langerhans of ordinary size from the pancreas of tumor-bearing rats, on the other hand, usually exhibited a normal (biphasic) IRI release pattern in response to glucose. Analysis by gel filtration suggests that the predominant form of IRI released from perifused tumor preparations, under either basal or glucose-stimulated conditions, eluted at a rate corresponding to rat insulin.
mesh_terms: D000236:Adenoma / Q000378:metabolism*; D000818:Animals; D005947:Glucose / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism*; D008297:Male; D003012:Microbial Collagenase; D009374:Neoplasms, Experimental / Q000378:metabolism; D009536:Niacinamide; D051381:Rats; D013311:Streptozocin
chemical_list: D007328:Insulin; D009536:Niacinamide; D013311:Streptozocin; D003012:Microbial Collagenase; D005947:Glucose