Some characteristics of new tissue-binding proteins for metabolites of vitamin D other than 1,25-dihydroxyvitamin D

A Specific High-Affinity Binding Macromolecule for 1,25-Dihydroxyvitamin D 3 in Fetal Bone

“…Although 1,25-(OH)2-[:3H]D3 is distributed between 3.5S and 6S macromolecules in rat calvaria cytosol, it binds preferentially to the 3.5S component. A 5 to 6S protein which binds 25-OH-D3 in cytosol prepared from rat bone has been demonstrated by other investigators using ion exchange chromatography (16). Furthermore, a similar 5 to 6S binding protein for 25-OH-Dt has been demonstrated in all rat and chick tissues examined (3,17).…”

Temporal Lobe Aggression in Rats

“…A 5 to 6S protein which binds 25-OH-D3 in cytosol prepared from rat bone has been demonstrated by other investigators using ion exchange chromatography (16). Furthermore, a similar 5 to 6S binding protein for 25-OH-Dt has been demonstrated in all rat and chick tissues examined (3,17).…”

The Role of Phosphate in the Action of Vitamin D on the Intestine

“…However the potency of this sterol is comparable to that of 25-OHD3 and therefore could not account for the observed response (36,37). The presence in intestinal mucosa, as well as in essentially all other tissues, of a cytoplasmic protein witi high affinity and specificity for 16) is additional evidence that this sterol may play a significant role in normal cell metabolism.…”

“…The accumulation of phosphate has not been as extensively characterized-Saturation of an initial pool of [32PJphosphate does not appear to occur until [8][9][10][11][12][13][14][15][16] min. Distribution of tracer in cell water suggests an inorganic phosphate concentration comparable to that postulated for the cytoplasmic phosphate pool (31).…”

“…Indeed, the restoration ofblood Ca and phosphorus levels through appropriate dietary supplements significantly reverses this growth retardation but never to the same extent as that achieved by the repletion of the rachitic animal with vitamin D (14). The identification in essentially all tissues of a cytoplasmic protein which specifically binds 25-hydroxycholecalciferol (25-OHD3) with high affinity (15,16) suggests that vitamin D may influence cellular metabolism at a nonspecific or basic level which could result in increased tissue growth. In fact, 25-OHD3 has been shown to act directly on skeletal muscle in vitro to accelerate the accumulation of phos-phate and to subsequently stimulate the rate of protein synthesis (17).…”