L-692429 (MK-0751) is a benzolactam derivative and a nonpeptidyl growth hormone secretagogue (GHS) agonist. L-692429 binds to G protein-coupled receptor with a K_i of 63 nM^[1][2]. IC50 & Target: Growth hormone secretagogue (GHS)^[1][3] In Vitro: L-692429 stimulates intracellular calcium release, inositol phosphate (IP) turnover, cAMP-responsive element binding protein (CREB) activity, serum-responsive element activity and bioluminescence resonance energy transfer (BRET) activity with EC₅₀ values of 26 nM, 47 nM, 60 nM, 63 nM and 58 nM, respectively^[2].
HeLa-T4 cells transiently expressing the flag epitope-tagged growth hormone secretagogue (GHS) receptor are treated with L-692429. The release of intracellular calcium is measured using fluorometry with the calcium indicator dye fluo-3/AM. Untransfected HeLa-T4 cells are unresponsive to L-692429 treatment, whereas HeLa-T4 cells transiently expressing GHS receptors demonstrate an increase in fluorescent emission after L-692429 treatment. A significant increase in luciferase activity after L-692429 treatment is seen, suggesting that activation of the GHS receptor stimulates the MAPK pathway^[3]. In Vivo: When tested in anesthetized rats (Wistar rats), L-756867 inhibits L-692429 (100 μg/kg)-stimulated GH secretion in a dose-dependent manner. Complete inhibition is observed at an i.v. dose of 100 μg/kg of L-756867^[1].