Subcellular distribution of peroxidase activity in human thyroid tissue.

Abstract

Thyroid tissue was obtained from 14 patients requiring thyroidectomy: 8 adenomas; 2 neoplastic; 3 hyperthyroid; 1 congenital goitrous hypothyroidism, and at postmortem from an anencephalic neonate. Normal thyroid tissue was obtained from 4 of the patients with adenomas. Subcellular fractions were isolated, characterized and the distribution of thyroid peroxidase activity was measured by guaiacol peroxidation and by the iodination of bovine serum albumin (BSA). Normal guaiacol activity ranged from 3.3 to 23.5 GU/g thyroid. Activity was normal in 4 patients with adenomas: (embryonal, follicular and Hurthle), but was on the low side of normal in the patients with follicular nodules (colloid variant) and with thyroid cancer. It was normal in the 1 patient with a Hurthle cell adenoma which contained no thyroglobulin, as measured by sucrose gradient centrifugation and double diffusion in gel against an anti-thyroglobulin serum. It was about 2 times normal in the thyroid of the 1 neonate, and was much greater in the thyroid of 2 hyperthyroid patients. There was no detectable activity in the thyroid of a patient with a complete block in the biosynthesis of thyroxine. Guaiacol activity was totally confined to the “microsomal” fraction of the thyroid tissue, in particular the “rough endoplasmic reticulum,” in all patients except for those with hyperthyroidism and in one of the 4 normal specimens. In these 2 groups, 18 to 48% of the activity was “soluble” (in the 105,000 × g supernatant). Subcellular distribution of iodination activity roughly paralleled the distribution of guaiacol activity.