Increasing β-arrestin-mediated internalization of the FSH-R does not change ERK phosphorylation. A. FSH-R internalization after 8 minutes of 125I-FSH exposure. Cells were transfected in sexplicates with the FSH-R and with 2 μg β-arrestin 1 or β-arrestin 2 or of empty plasmid. B: Kinetics of FSH-R internalization in the absence (diamonds) or presence of overexpressed β-arrestin 1 (squares) or β-arrestin 2 (triangles). C: immunodetection of P-ERK and of endogenous β-arrestin 1 or 2 as indicated, following 6 min of FSH exposure. The percentage +/- S.E.M. of FSH-R internalization in the presence of 50 or 200 ng of β-arrestins is indicated below the autoradiograms. D: Quantification of P-ERK (n = 4 independent experiments) in response to 6 min of FSH stimulation.