Developmental changes of parathyroid hormone/parathyroid hormone-related peptide and calcitonin receptor binding properties in the chicken calvaria and kidney

The equilibrium dissociation constant (K-d) and the maximum binding capacit y (B-max) of receptors for parathyroid hormone (PTH)/parathyroid hormone-re lated peptide (PTHrP) and calcitonin (CT) in the membrane fraction of the c alvaria and the kidney of chickens were examined from 1 d after the hatch u p to 24 wk of age by the use of radioligand binding assays. The K-d values of the PTH/PTHrP receptor in both tissues were decreased at 10 and 24 wk in female birds, whereas the values were increased at 24 wk in male birds. Th e B-max values of the PTH/PTHrP receptor in both tissues were decreased at 10 wk and returned to baseline at 24 wk in female birds. The values were in creased at 24 wk in male birds. The K-d and B-max values of CT receptors in the both tissues were constant during the experimental period in female an d male birds. The results suggest that the binding properties of PTH/PTHrP receptor and of CT receptor may be influenced by gonadal hormones relating to sexual maturation.