Presence of calcitonin receptors in shell gland of the guineafowl and changes in binding property during an oviposition cycle

Radioligand binding assays of membrane fraction of the shell gland endometrium. of guineafowl. revealed the presence of receptor for calcitonin. The equilibrium dissociation constant (K-d) obtained by Scatchard analyses was 0.50 to 1.25 nM in laying birds and 1.12 to 1.19 nM in nonlaying birds. The maximum binding capacity (B-max) per milligram of protein was 33.1 to 107.5 femtomoles in laying birds and 101.4 to 114.9 femtomoles in nonlaying birds. Both K-d and B-max values changed during eggshell formation in laying birds. The results suggest that calcitonin receptor binding may be related to eggshell formation in guineafowl.