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H F DeLuca

Publications and source records attributed to H F DeLuca.

At least 613 records · Page 34Linked to original sources
PubMed1974

Stimulation of 24,25-dihydroxyvitamin D3 production by 1,25-dihydroxyvitamin D3.

Vitamin D-deficient rats produce [(3)H]1,25-dihydroxyvitamin D(3) from [(3)H]25-hydroxyvitamin D(3) regardless of dietary content of calcium or phosphate. A daily dose of 130 picomoles of 1,25-dihydroxyvitamin D(3) for a period of 5 days reduces production of [(3)H]1,25-dihydroxyvitamin D(3) to essentially zero and stimulates production of [(3)H]24,25-dihydroxyvitamin D(3). A daily dose of 325 picomoles of 25-hydroxyvitamin D(3) has a similar but less dramatic effect. On the other hand, 650 picomoles daily of 24,25-dihydroxyvitamin D(3) given to vitamin D-deficient rats had no effect. Thus it appears that 1,25-dihydroxyvitamin D(3) is an important factor in the regulation of kidney metabolism of 25-hydroxyvitamin D(3).

Animals↗
PubMed1974

The acute effect of 25-hydroxycholecalciferol on renal handling of phosphorus. Evidence for a parathyroid hormone-dependent mechanism.

The acute effect of i.v. and direct intrarenal arterial infusion of 25-hydroxycholecalciferol (25HCC) and 1,25-dihydroxycholecalciferol (1,25-DHCC) on renal handling of phosphorus was evaluated in the following groups of rats: (a) intact animals, (b) parathyroidectomized (PTX) hypocalcemic rats, (c) PTX rats in which normocalcemia was maintained with calcium supplements and (d) PTX animals in which urinary phosphorus was augmented by (i) i.v. sodium phosphate, (ii) expansion of the extracellular fluid volume with normal saline, and (iii) i.v. parathyroid hormone (PTH). Clearances of inulin (C(In)), phosphorus (C(P)), and fractional clearances of phosphorus (C(P)/C(In)) of the experimental groups were compared with those of the corresponding control groups, and the clearances of the infused kidneys with those of the contralateral kidneys. In intact animals, i.v. 25HCC decreased C(P)/C(In) from 0.29+/-0.04 (mean +/-SE) to 0.19+/-0.04, and i.v. 1,25-DHCC decreased C(P)/C(In) from 0.25+/-0.04 to 0.15+/-0.02. The intrarenal infusion of both 25HCC and 1,25DHCC into intact animals failed to produce a unilateral change; however, it decreased C(P)/C(In) bilaterally. i.v. and intrarenal infusions of 25HCC or 1,25DHCC in PTX hypocalcemic and normocalcemic rats, and i.v. infusions of 25HCC in PTX rats receiving either sodium phosphate or normal saline, all failed to produce significant changes in C(P)/C(In). In contrast, 24HCC given i.v. to PTX animals receiving exogenous PTH was associated with a significant fall in C(P)/C(In), from 0.34+/-0.08 to 0.13+/-0.02. These results indicate that 25HCC enhances tubular reabsorption of phosphorus in rats, only in the presence of either endogenous or exogenous circulating PTH, but not in its absence and thus imply a PTH-dependent mechanism of 25HCC action on the kidney. This effect does not appear to be related to the conversion of 25HCC into 1,25DHCC, since the latter fails to affect tubular reabsorption of phosphorus in PTX rats.

Animals↗
PubMed1974

Liquid-gel partition chromatography of vitamin A compounds; formation of retinoic acid from retinyl acetate in vivo.

A clear separation of retinol, retinal, and retinoic acid has been achieved by liquid-gel partition chromatography on Sephadex LH-20 with solvent mixtures of chloroform, Skellysolve B, and methanol. A mixture of retinyl esters, retinol, retinal, and retinoic acid has been resolved on hydroxyalkoxypropyl Sephadex using Skellysolve B and acetone. There is no decomposition of any of the vitamin A compounds during chromatography, and recovery is complete. The combination of mildness and potential for resolution makes liquid-gel partition chromatography a superior tool for the separation of vitamin A compounds. This method has been applied to the study of vitamin A metabolism at physiological levels in the vitamin A-deficient rat. Retinyl palmitate, an ester of retinoic acid, retinal, retinol, retinoic acid, and a polar metabolite have been demonstrated in various tissues of the rat 12 hr after a dose of 2 micro g of [11-(14)C]retinyl acetate.

Acetates↗
PubMed1973

Intestinal calcium transport: stimulation by low phosphorus diets.

Rats maintained on a low phosphorus diet supplemented with 25-hydroxyvitamin D(3) show high intestinal calcium transport activity as compared to rats similarly treated but fed a diet containing adequate phosphorus. This increased transport activity is correlated with an increased biosynthesis of 1,25-dihydroxyvitamin D(3), the probable metabolically active form of the vitamin in the intestine.

Animals↗