Endocrinology, Vol 122, 1021-1026, Copyright © 1988 by Endocrine Society

ARTICLES

Polarized thyroid cells in monolayers cultured on collagen gel: their cytoskeleton organization, iodine uptake, and resting membrane potentials

N Takasu, S Ohno, M Takasu and T Yamada
Department of Gerontology, Endocrinology, and Metabolism, Shinshu University School of Medicine, Nagano-ken, Japan.

Porcine thyroid cells were cultured on collagen gel-coated cover glasses. They were reorganized into polarized monolayer cells; the basal cell membranes were in contact with the collagen gel, and the apical ones faced the culture medium. We studied cytoskeleton organization, resting membrane potentials, and iodine uptake of these cells. The quick-freezing and deep-etching replica method provided three-dimensional images of the cytoskeleton organization. Networks of microfilaments were observed under the apical cell membrane. In the deep cytoplasm and near the basal cell membranes, intermediate filaments predominated and were interlinked with the microfilaments. When the cells were cultured in the presence of TSH, TSH induced the formation of microvilli at the apical cell membranes and the accumulation of microfilaments under these membranes; in the deep cytoplasm, the intermediate filaments were more closely interlinked with the microfilaments. The microfilaments were immunostained with antiactin antibody. Thus, collagen is a factor in determining the cell polarity, and TSH further augments polarization through reorganizing the cytoskeletons. Electrophysiological study revealed that the resting membrane potential of cells cultured in the absence of TSH was -46 mV, and that of cells cultured in the presence of TSH was -58 mV. TSH hyperpolarized resting membrane potentials. These cells took up iodine. TSH in the medium augmented this uptake. TSH augments thyroid cell polarization through reorganizing the cytoskeletons and hyperpolarizing the resting membrane potentials and enhances iodine uptake by the cells.