Specific binding of 1α,25 dihydroxyvitamin D3 [1α,25 (OH)2D3] to macromolecular components in the cytoplasm and nucleus is demonstrated in parathyroid glands of vitamin D deficient chicks. The interaction of 1α,25 (OH)2D3 with the cytoplasmic binding component is of high affinity (Kd = 3.2 x 10-10 M) and high specificity [1α,25 (OHO)2D3 > 25 hydroxyvitamin D3 > 1 α hydroxyvitamin D3 > vitamin D3 in competing with radioactive 1α,25 (OH)2D3]. Both cytoplasmic and nuclear hormone macromolecular complexes sediment at 3.1S in 0.3 M KCl sucrose gradients, and agarose gel filtration of the components indicates an apparent molecular weight of 58,000. The 3.1S binding molecules are not observed in adrenal gland, testes, liver or kidney, but similar receptors for 1α,25 (OH)2D3 have been found previously in intestine. Macromolecular species with a high affinity and preference for 25 hydroxyvitamin D3 [25(OH)D3] are also identified in parathyroid cytosol and differ from the parathyroid 1α,25 (OH)2D3 binding component in that: (1) they sediment at 6S in 0.3 M KCl sucrose gradients, (2) they are observed in all tissues examined, (3) they have a higher affinity for 25 (OH)D3 than 1α,25 (OH)2D3 and (4) they are not found in the nucleus of the parathyroid glands, in vitro. The discovery of unique 1α,25 (OH)2D3 binding components in the parathyroid glands is consistent with the sterol hormone's action at this endocrine site and possible involvement in the regulation of parathyroid hormone synthesis and secretion.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Jan 1 1975|
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