Arf6 peptides inhibit LH/CGR desensitization by reducing β-arrestin release stimulated by 100 μM GTP. Membranes were preincubated with indicated concentrations of Myr-Arf6(2–13) peptide (A), non-Myr-Arf6(2–13) peptide (B), or Myr-Arf1(2–17) peptide (C) followed by the two-stage AC reaction. Results are means ± SEM of quadruplicate determinations from a single experiment and are representative of two or three separate experiments. For D, membranes were incubated with indicated treatments, diluted, and pelleted (see Fig. 3A legend); washed membranes were subjected to a two-stage AC reaction and to SDS/PAGE and Western blot analyses (see Fig. 3C legend). Results are means ± SEM of quadruplicate determinations from a single experiment and are representative of three separate experiments. Different AC activities reflect, in part, different membrane preparations.