The role of PTX-sensitive G-proteins in p38MAPK (A, B, C), JNK1/2 (D, E, F) and ERK1/2 (G, H, I) activation by H3 relaxin, H2 relaxin or R3(BΔ23–27)R/I5 in CHO-RXFP3 cells. Cells were pretreated with PTX (100 ng·mL–1) for 18 h prior to stimulation with peptides for up to 30 min. Phosphorylation of p38MAPK (A, B, C), JNK1/2 (D, E, F) and ERK1/2 (G, H, I) was quantified using the appropriate phospho-‘kinase'-specific Surefire AlphaScreen kit. Activation of p38MAPK, JNK1/2 and ERK1/2 by H3 relaxin (A, D, G) or H2 relaxin (B, E, H) both at 10−6 M was blocked by PTX. R3(BΔ23–27)R/I5 (10−6 M) activated p38MAPK (C) and ERK1/2 (I) but not JNK1/2 (F); ERK1/2 but not p38MAPK activation was blocked by PTX pretreatment. Data are mean ± SEM for four to seven independent experiments. Data were analysed by Student's t-test. *P < 0.05; **P ≤ 0.05 & P ≥ 0.001; ***P < 0.001.