A transplantable insulinoma was developed in inbred albino rats of the NEDH strain. The original tumor, 1 cm in diameter, was removed from the pancreas of a male parabiont 566 days following 1000 rads (10 J/kg) of total body x-irradiation. The time required for implanted fragments to grow to 0.5-1.5 cm in diameter decreased from 5-8 months in the first generation to 2-5 months in the seventh generation. Successful transplantation in male animals followed for 4 or more months after transplantation was significantly greater than in female animals [ollowed for a similar period of time (96%to versus 69%). Lidt and electron microscopy revealed that the tumors consisted predominantly of well anulated beta cells. Ultrastructural studies also showed smal numbers of Dcells. Tumor extracts contained an average of 223 units of immunoreactive insulin and 25.9 fg of immunoreactive somatostatin per gram wet weight of tissue. Tumors generally produced increasingly profound hypoglycemia within 24 months following transplantation, with plasma glucose levels frequently falling to 40 mg/100 ml or lower prior to death. Removal of tumors from chronically hypoglycemic animals resulted in transient rebound hyperglycemia with plasma glucose levels above 300mg/100mlwithinthefirst24 rand a gradual decline to normal levels of 129 mg/100 ml in 24 days. These observations correlated with findings of marked atropy and degranulation of the beta cells in the pancreata of tumor-bearing animals, and with gradual return of normal light microscopic morphology following-tumor removal.Limitation of starting material has proven to be a serious obstacle in several important areas of pancreatic beta cell research. Although methods are available for isolating pancreatic islets by collagenase digestion and Ficoll gradient centrifugation, such procedures at best yield only a few milligrams of material (1, 2). This has made the preparation of subcellular fractions and the isolation of other constituents of the beta cell extremely difficult. Although a transplantable insulinoma developed several years ago in the hamster has provided relatively large amounts of tissue, the predominant cell types in this tumor remain unclear because the insulin content is extremely low and light microscopic sections fail to stain with appropriate aldehyde-type stains (3, 4).The present studies involve experiments with a recently developed radiation-induced transplantable rat insulinoma that has made available gram quantities of well-granulated beta cells with high insulin content (5). This material has already proven valuable for the isolation of messenger RNA for insulin synthesis (6, 7) and for the initiation of studies towards the development of a permanent line of insulin-producing cells (8, 9). The present report describes the method used to develop and to transplant this tumor, and its morphology, hormone content, and physiologic effects on host animals. The actions exerted by this insulinoma on the recipient's own pancreatic islet cells are also described.MATE...

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Adler (4) di B i d (5) Handley (8) Kaufmann (7) Kettle (8) Krumbhaar (9) Paget (10) Reichelman (11) Taylor (12) 374 2422 422 1078 240 930 735 670 677

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