Vitamin D3 metabolites in rat epididymis: high 24,25-dihydroxy vitamin D3 levels in the cauda region

Normal male rats received six subcutaneous injections of 8.0 pmoles of tritiated 25-hydroxy vitamin D3 ([3H]25(OH)D3) or one intrajugular injection of 8.0 pmoles of high specific radioactivity [3H]-25(OH)D3. Lipid extracts of several tissues including the reproductive organs were subjected to sephadex LH-20 chromatography to determine the tissue distribution of the injected material and of the in vivo produced dihydroxylated cholecalciferol metabolites. The nature of the putative 25(OH)D3 and the 24,25-dihydroxy vitamin D3 (24,25(OH)2D3) from epididymis tissue was confirmed by high performance liquid chromatography (HPLC). The epididymis levels of 24,25(OH)2D3 were considerably higher in the cauda epididymis compared to kidney and caput epididymis levels. The other metabolites levels in this tissue were similar to those determined in the kidneys. The amounts of the three metabolites found in all other tissues were well below the cauda epididymis or kidney levels. The findings suggest a possible physiological role for 24,25(OH)2D3 in the epididymis, and are also consistent with data of others which indicated a possible action of 1,25-dihydroxy vitamin D3 (1,25(OH)2D3) in rat reproductive tissues.