Figure 1

Specific β-AR binding sites expressed on UROtsa cell membranes. UROtsa cell membranes were incubated with increasing amounts of ¹²⁵I-CYP in the absence and presence of 10 μM propranolol to determine total and nonspecific binding, respectively. Specific ¹²⁵I-CYP binding was plotted versus the amount of free radioligand concentration and fitted to a rectangular hyperbola using non-linear regression analysis. From this curve fit the number of specific ¹²⁵I-CYP binding sites was determined to be 951 ± 43 fmol/mg protein. In addition, the equilibrium dissociation constant of ¹²⁵I-CYP for these binding sites was calculated to be 32.4 ± 1.1 pM. Values are presented as the mean ± S.E. for n = 3 experiments performed in duplicate.