title: Somatostatin-like immunoreactivity in transplantable medullary carcinoma of rat thyroid: partial chromatographic and biological characterization.
abstract: Somatostatin-like immunoreactivity (SRIF-LI) has previously been demonstrated immunohistochemically in rat thyroid parafollicular cells. Studies were therefore performed to determine whether SRIF-LI was present in a transplantable medullary carcinoma of the thyroid (MCT) in the WAG/Rij strain of rat. SRIF-LI was found in MCT in significantly higher concentrations than in normal thyroid tissue. Thyroid and MCT SRIF-LI showed parallelism with the synthetic SRIF and RIA displacement curves and coeluted with synthetic SRIF on immunoaffinity chromatography. On gel filtration, thyroid SRIF-LI and the major peak of MCT SRIF-LI coeluted with synthetic SRIF. SRIF-LI of a larger molecular size was also present in the MCT. MCT and thyroid SRIF-LI coeluted with synthetic SRIF on high pressure liquid chromatography. MCT SRIF-LI purified by affinity chromatography was equipotent to synthetic SRIF in inhibiting dibutyryl cAMP-stimulated GH release by rat pituitary cells in monolayer culture. Serum SRIF-LI was elevated in tumor-bearing rats and showed characteristics similar to those of MCT SRIF-LI and synthetic SRIF on affinity and high pressure liquid chromatography (HPLC). Tumor-bearing rats showed diminished secretion of insulin after orally administered glucose and impaired secretion of GH in response to pentobarbital compared to normal control rats. The results indicate that SRIF-LI is produced in excessive quantities by a transplantable rat MCT and impairs the secretion of GH and insulin. The immunological, chromatographic, and biological properties of MCT SRIF-LI suggest that it is indistinguishable from synthetic SRIF.
mesh_terms: D000818:Animals; D002277:Carcinoma / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology; D013006:Growth Hormone / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D009368:Neoplasm Transplantation; D010424:Pentobarbital / Q000494:pharmacology; D011863:Radioimmunoassay; D051381:Rats; D013004:Somatostatin / Q000378:metabolism*; D013961:Thyroid Gland / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000378:metabolism*; D014184:Transplantation, Homologous
chemical_list: D007328:Insulin; D013004:Somatostatin; D013006:Growth Hormone; D010424:Pentobarbital; D005947:Glucose