No abstract

No abstract

No abstract

No abstract

No abstract

1. A comparison was made of the nature and intestinal intracellular distribution of the metabolites formed in vitamin D-deficient chicks from [4-(14)C]cholecalciferol and [1-(3)H]cholecalciferol. 2. The simultaneous administration of the two radioactive substances showed the presence in blood, liver, intestine, kidney and bone of cholecalciferol, its ester, 25-hydroxycholecalciferol and a further metabolite of cholecalciferol more polar than 25-hydroxycholecalciferol. The (3)H/(14)C ratios in these four radioactive components were the same as that of the dosed material (4.7:1) with the exception of the most polar material. The (3)H/(14)C ratio was lower in the fourth, most polar, metabolite (0.4:1-1.8:1) in all tissues examined, with the exception of blood. 3. In the chick intestine the polar metabolite accounted for almost 70% of the radioactivity in this tissue after a dose of 0.5mug. of [4-(14)C,1-(3)H]cholecalciferol. This polar metabolite from the intestine also had the lowest (3)H/(14)C ratio of all the tissues. It appears that in the chick intestine the polar metabolite reaches a maximum concentration of 1ng./g. of tissue, above which it cannot be increased irrespective of the dose of the vitamin. 4. The intestinal intracellular organelle with the highest concentration of (14)C radioactivity is the nucleus, and this radioactivity is almost entirely due to the polar metabolite with the lowered (3)H/(14)C ratio, in this case <0.2:1. It appears to be further localized in the chromatin of the nuclei. However, about half of the polar metabolite in the intestine is extranuclear. 5. Double-labelled 25-hydroxycholecalciferol was prepared and after its administration to vitamin D-deficient chicks the polar metabolite with the lowered (3)H/(14)C ratio was detected in liver, kidney, intestine, bone, muscle and heart. 6. None of the polar metabolite with the lowered (3)H/(14)C ratio was detected 16hr. after dosing with either the double-labelled vitamin or the double-labelled 25-hydroxycholecalciferol in blood and adipose tissue of vitamin D-deficient chicks, nor in the intestine, liver and kidney of supplemented birds. 7. The reasons for this loss of (3)H relative to (14)C are discussed in relation to possible chemical structures of this new polar metabolite.

No abstract

911 Comment Increases in osteoid volume with sodium fluoride, calcium, and vitamin D treatment are well documented. Small decreases in mineralisation rate have also been reported.2 But osteomalacia in the presence of high plasma 25-OHD concentrations has not been described in patients treated with this regimen. The plasma 1,25-(OH)2D3 concentration in our patient was just below the lower limit of normal, but the total plasma 1,25-(OH)2D (1,25-(OH)2D2-+1,25-(OH)2D3) concentration was probably normal since she was taking vitamin D2 and the radioimmunoassay did not measure plasma 1,25-(OH)2D2. The mechanisms by which fluoride may produce osteomalacia despite high plasma 25-OHD concentrations require further investigation. Possibilities include fluoride-induced end-organ resistance in bone to active vitamin D metabolites or an effect of fluoride on processes of bone mineralisation that are unaffected by vitamin D metabolites. Alternatively, fluoride might affect the metabolism of 25-OHD to other metabolites. Although lack of calcium supplements was probably unimportant in our patient, since the plasma calcium concentration remained above 2 40 mmol,l throughout treatment and dietary calcium intake was adequate, we cannot exclude it as a factor in the development of osteomalacia. Our results indicate that vitamin D in doses that produce high plasma 25-OHD concentrations does not protect against fluoride-induced mineralisation defects and that patients treated with this regimen require careful supervision. Trans-iliac biopsy provides a sensitive method for diagnosing generalised bone disease such as osteomalacia and may be necessary to detect its development when, as in our patient, plasma biochemical changes are not diagnostic. We thank J Sainsbury Ltd and the Special Trustees, St Thomas's Hospital, for generous financial support, and Dr T L Clemens, the Middlesex Hospital, London, WI, for 1,25-(OH)2D3 assays. Jowsey J, Riggs BL, Kelly PJ, Hoffman DL. Effect of combined therapy with sodium fluoride, vitamin D and calcium in osteoporosis. AmJ Med 1972 ;53 :43-9. 2 Meunier PJ, Bressot C, Vignon E, et al. Radiological and histological evolution of post-menopausal osteoporosis treated with sodium fluoride, vitamin D, and calcium. Preliminary results. In: Courvoisier B, Donath A, Baud CA, eds. Fluoride and bone. Berne: Hans Huber, 1978:263-76. 3Cass RM, Croft JD, Perkins P, Nye W, Waterhouse C, Terry R. New bone formation in osteoporosis following treatment with sodium fluoride.