Effect of thyrotropin on cell orientation and follicle reconstruction in rotated suspension culture of hog thyroid cells.

Isolated porcine thyroid cells were cultured in suspension by rotation on a gyratory shaker. In the absence of TSH, the cells associated into small, globular, and hollow aggregates or pseudofollicles and had microvilli only at the outer surface of the pseudofollicles which faced the culture medium. These pseudofollicles were inactive in terms of thyroglobulin synthesis and iodination. In the presence of TSH, cell aggregates were enlarged to 1 mm in diameter. Inside the aggregates. Inside the aggregates, the cells were reorganized into numerous functional follicles in which microvilli were oriented towards the follicular lumen. In both the presence and absence of TSH, Golgi apparatuses were found in the cytoplasm near the cell periphery bearing microvilli. These findings indicate that the TSH effects on thyroid cell morphology are to arrange the polarity of follicular cells in a proper direction and to enlarge the aggregates they form.