Effects of monensin on subcellular structure, thyroglobulin secretion and peroxidase activity of cultured thyroid...

The effects of monensin on subcellular structure, release of thyroglobulin (TG) and peroxidase (PO) activity were investigated using primary cultures of thyroid cells obtained from patients with Basedow's disease (Basedow's cells). TG concentration in the culture medium was measured by a sandwich enzyme immunoassay and the amount of TG in cultured cells was measured with an identical sandwich enzyme immunoassay after lysis of the cells with Triton X-100. PO activity of cultured cells was measured by a biochemical method. Addition of TSH (10 mU/ml/day) to the culture medium increased the synthesis and release of TG. When monensin (1 micron/l) was added to the medium on the last day of a 3-day incubation with TSH, the Golgi complex showed vacuolative change ultrastructurally, and the amount of intracellular TG was increased, whereas the amount of TG in the culture medium and PO activity became lower than those in the control group. These results suggest that in cultured Basedow's cells, TG is secreted through the Golgi complex, and that the activity of PO is elevated after processing in the Golgi complex.