1,25-dihydroxyvitamin D-3 inhibits parathyroid hormone-related peptide mRNA expression in fetal rat long bones in culture

When fetal rat long bones are incubated in the presence of 10(-8) M 1,25-di hydroxyvitamin D-3 [1,25(OH)(2)D-3], steady-state parathyroid hormone-relat ed peptide (PTHrP) mRNA levels are decreased, This decrease is temporary: i t is observed as soon as after 3 h of exposure and leaches a nadir after 6 h. At that time, PTHrP mRNA levels are significantly lower in the experimen tal than in the control bones. However the inhibitory effect vanishes after 24 h, despite continuous exposure to 1,25(OH2)(2)D-3 for even 48 h. This i s the first report showing that PTHrP mRNA expression can be regulated in r at fetal long bones in vitro by 1,25(OH)(2)D-3.