Table 2

Comparison of the apparent association constants (Ka ) and EC50 values for the sCT analogues derived from binding competition for 125I-sCT and cAMP accumulation assays, respectively

SCT analogueKa EC50
B8-H10 CTR cloneG12-E12 CTR cloneB8-H10-CTR cloneG12-E12 CTR clone
m −1 m
sCT1.63  ± 0.34  × 107 3.33  ± 2.14  × 108 6.67  ± 2.73  × 10−9 1.49  ± 0.52  × 10−9
SDZ-220-235<1  × 106 <1  × 106 5.88  ± 2.20  × 10−8 9.26  ± 0.54  × 10−10
SDZ-218-686<1  × 106 <1  × 106 7.67  ± 2.90  × 10−8 7.33  ± 0.23  × 10−10
SDZ-216-7101.61  ± 0.23  × 107 5.55  ± 3.85  × 107 N.A.N.A.
SDZ-212-7692.95  ± 1.80  × 106 4.76  ± 2.76  × 106 ∼1  × 10−7M2-b N.A.
sCT-(8-32)<1  × 106 <1  × 106 ∼1  × 10−7 M2-b N.A.
SDZ-219-3794.83  ± 1.68  × 106 7.09  ± 3.82  × 106 ∼1  × 10−7M2-b N.A.
AC5126.62  ± 4.95  × 106 4.74  ± 2.81  × 106 ∼1  × 10−7 M2-b N.A.

  • 2-a Apparent association constants were derived using the program LIGAND (19) and are mean ± standard error (n ≥ 3).

  • ↵2-b Potencies of inverse agonists to reduce constitutive activity of the CTR.

  • N.A. no detectable activity.