Amyloid of medullary carcinoma of the thyroid; partial characterization

Amyloid was isolated from lymph node metastases of a medullary thyroid carcinoma. SDS electrophoresis and gel filtration revealed a major subunit protein of MW less than 10 000. This subunit was capable of forming fibrils when dialysed in a solution against water. The amino acid composition of the subunit differed unequivocally from that of calcitonin. The amyloid also differed from systemic amyloids, since it did not form a top layer when homogenized and, further, did not seem to contain significant amounts of tryptophane. Since the amyloid of medullary carcinoma of the thyroid showed definite similarities to islet amyloid it is concluded that these two amyloids form a special class.