Synthesis of [1,2-3H2]cholecalciferol and metabolism of [4-14C,1,2-3H2]- and [4-14C,1-3H]-cholecalciferol in rachitic rats and chicks

Abstract

[1,2-3H2]Cholecalciferol has been synthesized with a specific radioactivity of 508 mCi/mmol by using tristriphenylphosphinerhodium chloride, the homogeneous hydrogen catalyst. With doses of 125ng (5i.u.) of [4-14C,i-3H2]cholecalciferol the tissue distribution in rachitic rats ofcholecalciferol and its metabolites (25-hydroxycholecalciferol and peak P material) was similar to that found in chicken with 500ng doses of the double-labelled vitamin. The only exceptions were rat kidney, with a very high concentration of vitamin D, and rat blood, with a higher proportion of peak P material, containing a substance formed from vitamin D with the loss of hydrogen from C-1. Substance P formed from [4-14C,1,2-3H2]cholecalciferol retained 36% of 3H, the amount expected from its distribution between C-I and C-2, the 3H at C-1 being lost. 25-Hydroxycholecalciferol does not seem to have any specific intracellular localization within the intestine of rachitic chicks. The 3H-deficient substance P was present in the intestine and bone 1 h after a dose of vitamin D and 30min after 25-hydroxycholecalciferol. There was very little 25-hydroxycholecalciferol in intestine at any time-interval, but bone and blood continued to take it up over the 8h experimental period. It is suggested that the intestinal 3H-deficient substance P originates from outside this tissue. The polar metabolite found in blood and which has retained its 3H at C-1 is not a precursor of the intestinal 3H-deficient substance P.

Studies on the Renal Uptake of Vitamin D3 in the Mouse and the Quail

“…Eighteen days after the injection of labelled vitamin D, a considerable amount of radioactivity was still present in the kidney. Similar results have been reported in the rat (Norman and DeLuca 1963, Lawson et al 1971. Vitamin D, has been reported as not being excreted in the urine (Cruickshank et af.…”

“…There was a slow increase in the amount of steriod in the kidney upon the intravenous injections of vitamin D,, with a maximum being reached at 24 h. Most of the vitamin D, was present in a nonmetabolized form. Similar results have been reported in the rat (Norman and DeLuca 1963, Lawson et al 1971. The reason for the slow uptake in the kidney is not clear.…”

“…I n contrast to the situation in the mouse, the quail kidney was found to lack the ability to accumulate radioactivity above the level of the blood after the administration of labelled vitamin D,. A greater radioactivity has been reported to occur in the kidney after the administration of labelled vitamin D, in rats than in chicks (Lawson et al 1971). Thus birds may lack a specific accumulatory mechanism for vitamin D,, present in the renal proximal tubuli of mammals.…”

Vitamin D and Its Hydroxylated Metabolites in the Rat

“…Extracts were analyzed for chole calciferol metabolites using thin-layer chromatography (6) or Sephadex LH-20 (Pharmacia Fine Chemicals, Ltd.) column chromatography. The columns were equilibrated and devel oped with chloroform/petroleum ether/methanol (75:23:2,v/v) (10).…”

Vitamin D metabolite profiling using liquid chromatography–tandem mass spectrometry (LC–MS/MS)

“…It began with the application of radioactive vitamin D preparations, which though useful in identifying new metabolites, was limited by constraints posed by the use of radio-isotopes in humans and problems with endogenous body pools reducing the specific activity of administered radioactive vitamin D compounds [3,4,5]. By the mid-1970s, reliable clinical assays had been developed based upon extraction, with and without a step of chromatography and detection by a competitive-protein binding technique using DBP (Vitamin D binding protein) or VDR (vitamin D receptor) [1,2,6].…”