Immunocytochemical study of localization and traffic of thyroid peroxidase/microsomal antigen.

We studied the distribution of binding sites for anti-peroxidase monoclonal antibody and anti-microsomal antibodies on isolated human thyroid follicles and a human thyroid cell line. Both open follicles and cells were incubated first with antibodies at +4 degrees C, then with colloidal gold labelled protein A. The topography of the binding sites for monoclonal anti-peroxidase antibody corresponded closely to the expected cell surface distribution of endogenous thyroid peroxidase since labelling was observed at the apical cell surface of the follicles.

Forskolin stimulates cAMP production and the onset of the functional differentiation in the fetal rat thyroid in vitro.

Forskolin, a diterpen stimulating the adenylcyclase induces in vitro an accumulation of cAMP in thyroid glands explanted from 17 day-old rat fetuses. Thyroid glands from 15 day-old fetuses exposed to forskolin exhibit, within 24 hr, an active folliculogenesis and 125I fixation in follicular cavities. The results indicate that cAMP probably activates the onset of both morphological and physiological maturation in the fetal rat thyroid.

Evidence for a role of the cytoskeleton in the in vitro folliculogenesis of the thyroid gland of the fetal rat.

Thyrotropic hormone (TSH) or cAMP accelerate the formation of follicular cavities in the explanted thyroid gland of the 15-day-old rat fetus. Cytochalasin B or vinblastine and nocodazole or colchicine, which disorganize microfilamental and microtubular structures respectively, inhibit or completely block in vitro-induced folliculogenesis. Exposure of the thyroid tissue to lumicolchicine, a structural isomer of colchicine deprived of antimicrotubular activity, does not inhibit the activation of folliculogenesis induced by TSH.

Thyroid follicular morphogenesis mechanism: organ culture of the fetal gland as an experimental approach.

The morphological and physiological changes induced by organ culture and thyroid-stimulating hormone (TSH) stimulation in the rat fetal thyroid gland were studied. Organ culture increased Golgi activity which was further enhanced by TSH, subsequently facilitating the formation of intracellular lumina. TSH also raised the intracellular cAMP level.

Basement membrane maintenance in cultures of isolated thyroid follicles.

Follicles from adult rat thyroid glands were isolated by digestion with collagenase followed by sieving. Electron microscopic studies have shown that basement membrane was present around each one of the isolated follicles. Follicles were cultured in vitro with or without thyrotropin and fibronectin.