Phosphate transport by plasma membranes of enterocytes during development: role of 1,25-dihydroxycholecalciferol

The present studies were designed to investigate phosphate transport across the brush border and basolateral membranes of enterocytes and to determine the effect of 1,25-dihydroxycholecalciferol [1,25(OH)2D3] on these processes in suckling and adolescent rats. Vitamin D deficiency was induced in suckling rats by feeding pregnant dams a vitamin D-deficient diet 48 h after insemination; they were then kept in the dark. Vitamin D deficiency in the adolescent rats was induced by feeding the vitamin D-deficient diet to weanling rats for 4 wk. V max values for Na(+)-dependent phosphate uptake in the brush border membranes of vitamin D-deficient and 1,25(OH)2D3-injected suckling rats was 0.7 +/- 0.1 and 1.5 +/- 0.2 nmol.mg protein-1.10 s-1 (P less than 0.01), respectively; V max values in adolescent rats were 0.2 +/- 0.05 and 0.36 +/- 0.04 nmol.mg protein-1.10 s-1 (P less than 0.05), respectively. Vmax values for Na(+)-dependent phosphate uptake in basolateral membranes of vitamin D-deficient and 1,25(OH)2D3-treated suckling rats were 0.006 +/- 0.001 and 0.047 +/- 0.006 nmol.mg protein-1.10 s-1 (P less than 0.01).