Abstract
The absorption, distribution, excretion and metabolism of 2-^3H-1α-OH-D_3 (4.2 Ci/mmol) were studied in vitamin D deficient rats in comparison with the normal rats after oral or intravenous dosing. (1) Maximum blood level of administered radioactivity was observed at 8 hours after oral administration with apparent half life of 3.8 days. This blood level was higher than that in normal rat. (2) As in the normal rat, administered radioactivity was distributed relatively high in the liver, while any other specific distribution or accumulation was not observed in the another tissues, which was consistent to the finding in the normal rat. The tissue levels of the radioactivity were higher than these in the normal rat. (3) Urinary excretion of administered radioactivity was significantly higher, fecal and biliary excretion was significantly lower than that in the normal rat after intravenous dosing. (4) Relative percentage of ^3H-1α, 25-(OH)_2-D_3 content to ^3H-1α-OH-D_3 content in tissues and blood was higher than that in the normal one. Above results suggest that in the vitamin D deficient state, the tissue accumulation of 1α-OH-D_3 was significantly augmented than in the normal rat, thus resulting increased bioavailability of its active metabolite, 1α, 25-(OH)_2-D_3.
