HUMAN THYROID EPITHELIAL-CELLS CULTURED IN MONOLAYERS .1. DECREASED THYROGLOBULIN AND CAMP RESPONSE TO TSH IN 12-WEEK-OLD SECONDARY AND TERTIARY CULTURES

An in vitro system of secondary and tertiary cultures of human thyroid epithelial cells (TFECs) in monolayer is described. The function of t he cells was evaluated by the second messenger cAMP and the end produc t thyroglobulin (Tg). The Tg production from the cells was measured in the supernatant by a newly developed enzyme-linked immunosorbent assa y. The TFECs in secondary monolayer cultures had preserved the ability to produce Tg and cAMP despite lack of polarization. Furthermore, a p reserved ability of TSH-stimulated production of Tg and cAMP in 12-wee k-old secondary and tertiary cultures was found. However, the Tg and c AMP levels decreased gradually with the age of the cultures. In the se condary culture the TSH-stimulated Tg production decreased from 253 ng /mu g DNA (205-263) after 3 weeks to 18 ng/mu g DNA (6-81), P < 0.001, n = 6 after 12 weeks and TSH-stimulated cAMP production from 660 pmol /mu g DNA (500-840) to 60 (40-200), P < 0.001, n = 6. The decreased re sponsiveness of long-term cultures results in preference of short-term secondary cultures, which provide a more suitable experimental model for in vitro investigation of human thyroid cell functions.