A Comparison of the Responses of Lower Vertebrate Intestines to Prostaglandin $E_1\;and\;E_2$

1. The isolated strips of guinea-pig, fowl and reptiles (snake and tortoise) showed consistenly excitatory responses to $PGE_1\;and\;E_2$, which were dose-dependent. 2. Frog intestine revealed inhibitory responses to both $PGE_1\;and\;PGE_2$ except a small of $PGE_2$ (1-10 ng/ml) caused slight contraction. 3. The intestines of pieces showed inconsistent responses to $PGE_1\;and\;E_2$. In fresh-water fish(carp), $PGE_1$ produced relaxation under the dose of 50 ng/ml, and contraction by the large doses, but $PGE_2$ consistently caused contraction in dose-dependent manner. However, the strips of sea-water fish revealed the different responses to PGE compound: $PGE_1$ caused relaxation and $PGE_2$ conversly contraction even though in small degree. 4. These results that there are genera differences in the responses of the longitudinal strips of intestine to $PGE_1\;and\;PGE_2$ was assumed to be possibly correlated with evolutionally primitive function of gut.