TSH and catecholamines: independent effects on active transport and iodine organification in isolated thyroid cells.

Catecholamines greatly stimulated iodine organification in thyroid cells isolated by trypsinization but failed to increase the cell-medium (C/M) ratio of 131I- or 99mTcO4- in the same cells preparation. Both TSH and catecholamines increased the concentration of organified iodine in thyroid cell despite the presence of active transport inhibitors, suggesting either the existence of a second thyroidal transport system or the possibility of an accelerated entry of anions into thyroid cells in the presence of stimulatory agents.