Down-regulation of the alpha-2C adrenergic receptor: involvement of a serine/threonine motif in the third cytoplasmic loop

Table 2 Affinity of norepinephrine for the mutated alpha-2C adrenergic receptors expressed in CHO cells.

Clone	K_i, nM	Slope factor	n
Wild-type (SSTS)	184 ± 9	0.79	3
SSVA	90 ± 4^*	0.73	3
AAVA	71 ± 5^*	0.65	3

K_i values were derived based on a single-site model and are the geometric means of three independent inhibition experiments, each done in duplicate. The slope factor was determined in a separate analysis based on a variable slope model. The data were not consistently better fit by a two-site model than a one-site model for any of the three clones. The concentration of [³H]rauwolscine was 0.12 ± 0.01 nM. ^*Significantly different (p < 0.05) than wild-type based on a t-test of the pK_i values.