Potencies and inverse agonist efficacies of antagonists at hH2R-GsαS and gpH2R-GsαS expressed in Sf9 cell membranes
| Antagonist | hH2R-GsαS | gpH2R-GsαS | ||||
|---|---|---|---|---|---|---|
| KB | Rel. Pot. | Inv. Ago. Eff. | KB | Rel. Pot. | Inv. Ago. Eff. | |
| nM | nM | |||||
| 14(CIM) | 930 (460–1900) | 100 | −0.04 ± 0.04 | 1100 (400–2900) | 100 | −0.07 ± 0.08 |
| 15 (RAN) | 790 (270–2300) | 117 | −0.08 ± 0.041-150 | 570 (250–1300) | 192 | −0.17 ± 0.01 |
| 16 (ZOL) | 1000 (420–2400) | 93 | −0.06 ± 0.08 | 520 (270–960) | 211 | −0.12 ± 0.08 |
| 17 (TIO) | 60 (30–130) | 1550 | −0.04 ± 0.09 | 50 (30–90) | 2200 | −0.12 ± 0.08 |
| 18(FAM) | 29 (20–50) | 3200 | −0.07 ± 0.05 | 25 (10–40) | 4400 | −0.14 ± 0.12 |
| 19(APT) | 230 (70–760) | 404 | −0.21 ± 0.051-150 | 290 (160–530) | 379 | −0.09 ± 0.04 |
K B values for hH2R-GsαS and gpH2R-GsαS were determined in the GTPase assay. GTP hydrolysis was determined as described under Experimental Procedures. Reaction mixtures contained Sf9 membranes expressing fusion proteins, 1 μM HIS as agonist and antagonists at concentrations from 1 nM to 100 μM to generate saturated competition curves. Competition curves were analyzed by nonlinear regression. To determine the inverse agonist efficacies of antagonists (Inv. Ago. Eff.), the effects of antagonists at a fixed concentration (10 μM) on basal GTPase activity were assessed and referred to the stimulatory effect of 100 μM HIS (= 1.00). Typical basal GTPase activities ranged between ∼1 and 2 pmol/mg/min, and typical GTPase activities stimulated by HIS (1 μM) ranged between ∼2.5 and 5.0 pmol/mg/min. Data shown are the means of four to five experiments performed in duplicate. Numbers in parentheses represent the 95% confidence intervals. The relative potency (Rel. Pot.) of CIM was set at 100, and the potencies of other antagonists were measured against this value to facilitate comparison of antagonist potencies in the various systems. The effects of compounds at hH2R-GsαS were compared with the corresponding effects of compounds at gpH2R-GsαS using the t test.
↵1-150 , p < 0.05.