An important effect of TSH on prostacyclin concentration in porcine thyroid cells

Fresh thyroid slices obtained from normal pigs contained prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha) and prostacyclin (PGI2, measured as the end metabolite, 6-keto PGF1 alpha), but the concentrations of PGI2 exceeded those of PGE2 and PGF2 alpha. A preferential increase of PGI2 was produced when the slices were exposed to a large dose of TSH (thyroid-stimulating hormone). When thyroid cells were isolated and cultured in the absence of TSH, thyroidal concentrations of PGI2, PGE2 and PGF2 alpha were about equal. When the cells were acutely exposed to a large dose of TSH, intrathyroidal concentration of prostaglandin increased significantly, but the relative concentrations of prostaglandins were not markedly altered. When thyroid cells were cultured in the presence of a small dose of TSH, relative concentrations of thyroidal prostaglandins were comparable to those of fresh thyroid slices, as a result of a preferential increase of PGI2 and decreases of PGE2 and PGF2 alpha. Further increase of PGI2 was induced when the cells cultured with TSH were acutely exposed to a large dose of TSH. It is concluded that although cells contain PGE2, PGF2 alpha and PGI2, a preferential accumulation of PGI2 is found only when thyroid cells are chronically stimulated by TSH.