does pertussis toxin inhibit responses to cathine in capacitated spermatozoa?
Pertussis toxin, which blocks responses involving many inhibitory G subunits, has been shown to abolish the inhibitory effects of FPP in capacitated cells when assessed using CTC and cAMP analyses (Fraser and Adeoya-Osiguwa, 1999), as well as protein tyrosine phosphorylation (Adeoya-Osiguwa and Fraser, 2000). Given the similarity in responses obtained with cathine and FPP in both uncapacitated and capacitated spermatozoa, it seemed possible that inhibitory G subunits might be involved in responses to PPAs in capacitated spermatozoa. Earlier studies demonstrated that pertussis toxin had no detectable effect on either uncapacitated or capacitated suspensions when used alone and it only inhibited responses to FPP in capacitated cells (Fraser and Adeoya-Osiguwa, 1999). Since responses to PPAs mimic responses to FPP, we felt there was no need to test pertussis toxin on its own again. Capacitated suspensions were preincubated for 90 min and prepared as detailed in Materials and methods, then
