Table 2.

Palosuran lacks high affinity for recombinant hUT receptor expressed in intact cells: radioligand-binding affinity constants (K_i values, [¹²⁵I]hU-II competition) for human urotensin-II (hU-II), palosuran and SB-657510 at the recombinant hUT receptor in membrane and whole cell preparations

	Membrane binding Ki (nM; n=7)	Whole cell binding Ki (nM; n=4)	Relative affinitya
Urotensin-II	1.9±0.5	2.9±0.5	1.5
SB-657510	61.4±7.5	46.2±3.0	0.8
Palosuran	5.1±0.7	276.0±66.9***	54.1

Abbreviation: hUT, human urotensin-II receptor.

^aRelative affinity is expressed as the whole cell binding human UT K_i relative to the corresponding value obtained in hUT membrane preparations. All values are expressed as mean±s.e.mean. Membrane data are from Table 1 and are included for ease of comparison. Statistical comparisons were made using an unpaired, two-tailed t-test where ^***P<0.001 (versus K_i obtained for the corresponding ligand in membrane preparation).