Stimulatory effect of pertussis toxin on tissue cyclic AMP levels in canine thyroid slices

The in vitro effects of the protein purified from the culture medium of Bordetella pertussis (pertussis toxin) on cyclic AMP levels in canine thyroid slices were studied. The toxin caused a three-fold increase in tissue cyclic AMP levels after 18 h or longer incubation. Furthermore, when the slices were incubated with the toxin for 6 h and then incubated without the toxin for further 12 h, similar effects were observed. These results indicate that pertussis toxin elevates tissue cyclic AMP levels after a time lag in a manner different from other thyroid stimulators.