Figure 2. Functional characterization of lfGHRHR and xGHRHR₂.

Intracellular cAMP accumulation ([cAMP]_i) in response to 100 nM of GHRH and related peptides on CHO-K1 cells transfected with (A) lfGHRHR and (D) xGHRHR₂ (*** indicates P<0.001, ** indicates P<0.01, and * indicates P<0.05). Effects of GHRH and related peptides on graded concentrations of peptides on [cAMP]_i (B) lfGHRHR- and (E) xGHRHR₂-expressing cells. The intracellular calcium mobilization ([Ca²⁺]_i) assays of (C) lfGHRHR- and (F) xGHRHR₂-expressing cells. For [cAMP]_i, values represent mean ± SEM (n = 4). For ([Ca²⁺]_i, data were expressed in ΔRFU value (maximum changes in the fluorescence signals from baseline) and converted to percentage of the maximum of xGHRH-induced [Ca²⁺]_i elevation. Results are expressed as mean ± SEM from at least 10 independent experiments, cell number = 20 to 50. Peptide species: h, human; x, X. laevis, zf, zebrafish D. rerio; gf, goldfish C. auratus.