Inhibitory actions of polyphloretin phosphate and related compounds on the response to prostaglandin in the smooth muscle of guinea-pig stomach.

The inhibitory actions of polyphloretin phosphate (PPP) and related compounds, di-4-phloretin phosphate (DPP), PHLORETIN AND TRIHYDROXY PROPIOPHENONE (THPP) on the contractile responses to prostaglandin (PG) and acetylcholine (ACh) in longitudinal smooth muscle of guinea-pig stomach were studied. Of the four inhibitors PPP and DPP showed relatively selective antagonism for PGE1. DPP gave the highest pW2 value against PGE1. These results indicate that DPP is a useful antagonist of PG in smooth muscle, although it slightly inhibits responses to ACh, 5-HT or histamine, and the Ca-induced contracture in K depolarized preparation.