129 increased concentration of 25-hydroxyvitamin d (250) and 1,25 dihydroxyvitamin d (1,25) receptors in kidneys of rats treated with phenobarbital (pb)

Chronic administration of PB and other anticonvulsant drugs can induce hypocalcemia and osteopenia. A decreased plasma 25D concentration can be responsible, and maybe other derangements of 1,25D. The study of receptor concentration in a target tissue (kidney) will inform on the performance of vitamin D metabolites. Ten wistar rats were treated with PB (6 mg/Kg/d) from the 21st day of life for ten weeks. At this time, whole blood was obtained, both kidneys were removed for 25D and 1,25D receptor quantitation (Reinhart, Hollis 1986). Control group included 5 rats. Plasma values showed no differences apart from 25D which was respectively 8.3(2.4) and 5.2(2.3) ng/ml (p < 0.05). Raised concentration of 25D receptors is in agreement with low hepatic output. Converseley raised concentration of 1,25 receptors suggests a normal response for calcium reabsorption, and up-regulation response or a direct induction of PB over 1 α-hydroxilase, requiring further studies. CAICYT PM: 89-0018.