VITAMIN-D METABOLISM IN JAPANESE QUAIL - EFFECTS OF LEAD-EXPOSURE AND DIETARY CALCIUM

Four-week-old female Japanese quail were raised either on a low calcium (0.2%) or on a normal calcium (2.3 to 3.3%) diet for 15 days and at the same time they were given drinking water containing either lead acetate (0.032, 0.32, 3.2, or 16.0 mg Pb/ml) or sodium acetate (1.75 mg acetate/ml). On the 16th day, in vitro kidney production of 1,25- and 24,25-dihydroxyvitamin D3 [1,25-(OH)2D3 and 24,25-(OH)2D3] from tritiated 25-hydroxyvitamin D3, plasma calcium, and phosphate, and body retention of lead (plasma, liver and femur), were determined. Under both dietary conditions, lead ingestion (0.32, 3.2 and 16.0 mg Pb/ml), when compared with sodium acetate-treated controls, resulted in the stimulation of 1,25-(OH)2D3 production, but 24,25-(OH)2D3 increased only under normal dietary calcium and higher doses (3.2 and 16.0 mg Pb/ml) of lead. Production of 24,25-(OH)2D3 was non-detectable in all groups given low calcium diet. Lead added in vitro to kidney homogenates of untreated, age-matched quail had no significant effect on renal hydroxylases. Lead treatment also had no significant effect on plasma calcium and phosphate concentrations. The lead concentration in plasma, liver, and femur was always higher at comparable dose levels of lead under the low calcium dietary conditions. The data indicate that subacute lead ingestion results in the stimulation of renal 25-hydroxyvitamin D3-1-hydroxylase activity. © 1979.