Table 2

Affinity for the α_1b-adrenoceptor-GFP constructs and potency of phenylephrine to stimulate inositol phosphate generation

α_1b-Adrenoceptor-GFP Construct	K_i	EC₅₀
	μM	nM
Wild Type	30 ± 11	438 ± 9
3CAM	0.4 ± 0.05^2-a	2.0 ± 0.4^2-a
A293E	46 ± 12	80 ± 18^2-a
D142A	61 ± 24	180 ± 60^2-a
M8	34 ± 14	356 ± 54

The affinity of phenylephrine to bind to the various forms of the α_1b-adrenoceptor-GFP was estimated from competition binding experiments with [³H]prazosin and corrected for receptor occupancy by [³H]prazosin. EC₅₀values derive from stimulation of [³H]inositol phosphate production above basal levels. Data are presented as mean ± S.E. from three independent experiments.

↵2-a Significantly different from wild type,P < .01.