Comparison of in vivo and in vitro responses to sulfated and non-sulfated ceruletide

Responses of guinea pig gall bladder to sulfated and non-sulfated ceruletide were compared in vitro and vivo. Tested in vivo, sulfated ceruletide was 75 times more potent than non-sulfated. In vitro, sulfated was 150 times more potent. Thus, differences in potency are substantially less when tested in vivo, and reported differences in relative potency reflect not only chemical structure but also the method used for testing.