Table 1

Saturation analysis-derived binding constants of the three diverse radioligands for wild-type and mutant human tachykinin NK₂receptors expressed in CHO cells

Radioligand	Receptor Type
	Wild-type		His¹⁹⁸Ala		Tyr²⁶⁶Ala K_d	Tyr²⁶⁶Phe		Phe²⁷⁰Ala		Tyr²⁸⁹Ala K_d	Tyr²⁸⁹Phe
	K_d	B_max	K_d	B_max	Tyr²⁶⁶Ala K_d	K_d	B_max	K_d	B_max	Tyr²⁸⁹Ala K_d	K_d	B_max
[¹²⁵I]NKA	2.4 ± 0.4	206 ± 28	N.D.		N.D.	2.8 ± 0.2	211 ± 19	N.D.		N.D.	2.0 ± 0.3	199 ± 55
	(5)					(6)					(12)
[³H]SR 48968	0.3 ± 0.1	3274 ± 1489	4.8 ± 1.1	273 ± 43^1-150 ^, ^1-160	N.D.	1.2 ± 0.1	779 ± 101	1.6 ± 0.3	1230 ± 38	N.D.	N.D.
	(6)		(5)			(6)		(4)
[³H]MEN 11420	4.0 ± 0.4	1664 ± 416	11.5 ± 2.1	807 ± 82	N.D.	N.D.		N.D.		N.D.	2.9 ± 0.3	3636 ± 391
	(6)		(4)								(4)

K_d (nM) and B_max (fmol/mg protein) values are expressed as mean ± S.E.M. of the number of independent determinations indicated in parentheses.

N.D., no detectable binding.
↵1-150 P < .05 versus wild-type.
↵1-160 P < .05 versus [³H]MEN 11420.