Intrinsic activity of MC4 receptor agonists in cAMP accumulation, calcium mobilization, and receptor internalization assays Functional properties of agonists at FMC4 receptors expressed in HEK-293 cells were measured, respectively, by AlphaScreen, FLIPR, and FACS analysis as described under Materials and Methods. Intrinsic activity values are expressed as percentage of the maximal α-MSH response (mean ± S.E.M.). Data for γ-MSH in calcium and receptor internalization assays and NBI 55886 and NBI 56297 in the calcium assays are the observed activity at 1 μM. Data are n = 3 (cAMP accumulation), n = 6 (calcium mobilization), and n = 4 (receptor internalization).
cAMP Accumulation | Calcium Mobilization | Internalization | |
|---|---|---|---|
| α-MSH | 100 | 100 | 100 |
| β-MSH | 83 ± 13 | 94 ± 12 | 118 ± 9 |
| γ-MSH | 80 ± 7 | 62 ± 7 | 75 ± 5 |
| Des-acetyl-α-MSH | 84 ± 18 | 96 ± 9 | 107 ± 2 |
| NDP-MSHa | 112 ± 11 | 80 ± 7b | 89 ± 5 |
| THIQa | 98 ± 5 | 7 ± 3b | 29 ± 7c,d |
| NBI 55886a | 73 ± 17 | 40 ± 8 | 16 ± 2c |
| NBI 56297a | 81 ± 6 | 23 ± 7b | -5 ± 18c |
| NBI 56453a | 103 ± 8 | 7 ± 2b | 27 ± 20c |
| NBI 58702a | 110 ± 14 | 20 ± 5b | 38 ± 16c |
| NBI 58704a | 149 ± 15 | 23 ± 7b | 34 ± 11c |
↵ a ANOVA showed a significant influence of the different assays on intrinsic activity
↵ b Intrinsic activity was significantly different between cAMP accumulation and calcium mobilization assay
↵ c Intrinsic activity was significantly different between cAMP accumulation and receptor internalization assays
↵ d Intrinsic activity was significantly different between calcium mobilization and receptor internalization assays