TABLE 1

Agonist activity (EC50 and efficacy relative to SRIF-14) was assessed as the ability of the compounds to stimulate [35S]GTPγS binding in membranes of CHO cells expressing the human sst4 (CHO-h sst4)

Under routine testing conditions (100 mM NaCl and 10 μM GDP), SRIF-14 concentration dependently increased [35S]GTPγS binding to give fitted curve maxima of ∼110% over basal, whereas the corresponding value under lower NaCl and GDP conditions (20 mM NaCl and 3 μM GDP) was ∼45% over basal. Data represent means ± S.E.M. from at least three experiments. Representative curves for J-2156, compound A, SRIF-14, and CST-17 are shown in Fig. 1. Agonist activities of J-2156, SRIF-14, and LTT-SRIF-28 as determined in the presence of 100 mM NaCl and 10 μM GDP have been reported by us earlier (Engström et al., 2005).

100 mM NaCl, 10 μM GDP 20 mM NaCl, 3 μM GDP
EC50 Efficacy (normalized against SRIF-14) EC50 Efficacy (normalized against SRIF-14)
NM nM
J-2156 17 ± 1 340 ± 20 3.9 ± 1.0 300 ± 20
Compound A 15 ± 4 210 ± 10 3.4 ± 1.7 270 ± 40
LTT-SRIF-28 80 ± 15 120 ± 10 N.D. n.d.
SRIF-28 7.8 ± 1.9 110 ± 10 N.D. n.d.
SRIF-14 6.5 ± 0.7 100 4.4 ± 0.7 100
CST-17 46 ± 6 93 ± 7 27 ± 11 120 ± 20
  • N.D., not determined.