Table 2.

Competitive Binding and cAMP Accumulation Results at the hMCRs.

Peptides	MC1R				MC3R				MC4R				MC5R
	IC50 (nM)	% BE	EC50(nM)	Act %	IC50(nM)	% BE	EC50(nM)	Act %	IC50(nM)	% BE	EC50(nM)	Act %	IC50(nM)	% BE	EC50(nM)	Act %
1	105 ± 16	100	4.3 ± 0.2	100	63 ± 5	100	7.1 ± 0.1	100	359 ± 52	76	548 ± 58	100	109 ± 8	100	3.9 ± 0.6	63
2	50 ± 9	42	52 ± 4	100	>1000	15	120 ± 12	100	65 ± 6	58	928 ± 23	52	46 ± 4	44	37 ± 4	48
3	>1000	65	418 ± 69	100	>1000	80	255 ± 26	17	>1000	44	133 ± 3	46	NB	0	NA	0
4	243 ± 36	33	25 ± 3	100	>1000	13	315 ± 38	100	>1000	13	280 ± 34	58	NB	0	NA	0
5	339 ± 31	49	10 ± 0.7	100	90 ± 7	62	252 ± 26	85	835 ± 119	43	407 ± 28	79	37 ± 4	37	>1000	44
6	122 ± 16	81	6.5 ± 0.7	100	>1000	45	116 ± 13	87	>1000	8	17 ± 2	55	NB	0	433 ± 60	52
7	154 ± 9	61	11 ± 1	100	224 ± 25	51	57 ± 12	93	53 ± 10	46	36 ± 4	79	NB	0	>1000	33
8	NB	0	NA	0	>1000	65	NA	0	NB	0	NA	0	NB	0	NA	0
9	0.74 ± 0.26	28	>1000	46	46.8 ± 0.7	35	>1000	56	NB	0	NA	0	NB	0	NA	0
10	NB	0	NA	0	>1000	33	NA	0	2.1 ± 0.4	22	NA	0	NB	0	NA	0
11	1.9 ± 0.01	18	3 ± 0.3	63	>1000	35	>1000	23.1	NB	0	NA	0	NB	0	NA	0
12	80 ± 15	30	>1000	39	>1000	76	>1000	23.1	10 ± 1	52	NA	0	NB	0	NA	0
MT-II	1 ± 0.1	100	1 ± 0.4	100	2.0 ± 0.1	100	5.1 ± 0.3	100	2.3 ± 0.85	100	2 ± 0.6	100	4 ± 1	100	6 ± 2	100

MT-II, Ac-Nle-c[Asp-His-D-Phe-Arg-Trp-Lys]-NH₂, is used as a control for the entire assays. IC₅₀ = concentration of peptide at 50% specific binding (N = 3). NB = 0% of [125I]-NDP-α-MSH displacement observed at 10 μM %BE (binding efficiency) = maximal % of [¹²⁵I]-NDP-α-MSH displacement observed at 10 μM. EC₅₀ = Effective concentration of peptide that was able to generate 50% maximal intracellular cAMP accumulation (N = 3). Act% = % of cAMP produced at 10 μM ligand concentration, in relation to MT-II. NA = 0% cAMP accumulation observed at 10 μM. The peptides were tested at a range of concentrations from 10⁻¹⁰ to10⁻⁵ M.