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. Author manuscript; available in PMC: 2019 Aug 28.
Published in final edited form as: Am J Physiol Regul Integr Comp Physiol. 2017 Dec 6;314(4):R574–R583. doi: 10.1152/ajpregu.00372.2017

Table 1.

Effects of age on high- and low-affinity binding sites for ICI-118,551 and ICI-89,406 in rat liver particulates

Ligand Competing for (—)-[125I]Iodopindolol Binding
ICI-118,551
 ICI-89,406
Young Old P value Young Old P value
RH, fmol/mg 2.34 ± 0.82 7.17 ± 2.85 0.165 2.30 ± 0.30 3.24 ± 1.12 0.450
RL, fmol/mg 1.90 ± 0.33 2.83 ± 0.83 0.346 2.48 ± 0.83 3.73 ± 1.11 0.399
%RH 51.7 ± 5.8 68.1 ± 2.9 0.064 53.8 ± 11.5 44.3 ± 3.0 0.478
%RL 48.3 ± 5.8 31.9 ± 2.9 0.064 46.2 ± 11.5 55.7 ± 3.0 0.478
KH, nM 2.13 ± 1.31 9.05 ± 5.80 0.309 0.50 ± 0.09 0.86 ± 0.49 0.528
KL, µM 1.14 ± 0.76 12.97 ± 9.13 0.266 7.55 ± 6.19 3.72 ± 0.46 0.581

Values are means ± SE from 4 young and 5 old rats. RH and RL, nos. of sites binding ICI-118,551 or ICI-89,406 with high and low affinity; KH and KL, dissociation constants of high- and low-affinity binding sites. Competition binding curves using liver particulate preparations from young (3–6 mo old) and old (24 mo old) rats were constructed as described in Fig. 2, and the data were analyzed with a weighted, nonlinear, least-squares curve-fitting program (38). ICI-118,551 and ICI-89,406 competition curves were best fit by a 2-site model describing high- and low-affinity binding sites.