Extracts of transplantable rat medullary thyroid carcinomas were fractionated by concanavalin A-agarose chromatography and SDS-polyacrylamide gel electrophoresis. While tumor extracts contained mostly (>90%) native calcitonin, 4 distinct larger calcitonin species (M(r) = 27,000, 17,000, 13,700, and 9,600) were also observed. Glycoprotein fractions from lectin-affinity chromatography of the tumor extracts contained 0.3-1.5% of the total immunoreactive calcitonin. Gel electrophoresis of the pooled glycoprotein fractions demonstrated that the predominant forms of immunoreactive calcitonin were larger than calcitonin monomer. One high molecular weight species (M(r) = 9,600), isolated in sufficient quantity from the polyacrylamide gels for reapplication to concanavalin A-agarose, was specifically eluted from the lectin, indicating that it was a glycoprotein. These results are the first evidence that intact C-cells contain at least one high molecular weight glycoprotein form of immunoreactive calcitonin and suggest that addition and removal of carbohydrate side chains occur during processing of calcitonin precursors to the native hormone.
|Number of pages||3|
|State||Published - Jan 1 1981|
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism