Prostaglandin inactivation in guinea-pig lung and its inhibition

1 Several compounds were tested for their ability to inhibit prostaglandin metabolism in guinea-pig lungs.2 In isolated perfused lungs polyphoretin phosphate (PPP) inhibited prostaglandin metabolism being active at concentrations greater than 100 ng/ml and having an ID(50) of 2.15 mug/ml against prostaglandin E(2) metabolism and 1.55 mug/ml against prostaglandin F(2alpha) metabolism.3 At these doses no antagonism of the actions of prostaglandins was seen.4 Diphloretin phosphate (DPP) was more active on a weight for weight basis and inhibition of inactivation of prostaglandins was seen at concentrations greater than 10 ng/ml, the ID(50) being 0.54 mug/ml against both prostaglandins E(2) and F(2alpha).5 At concentrations greater than 5 mug/ml DPP antagonized the actions of prostaglandin F(2alpha).6 The sulphydryl-binders N-ethyl maleimide (NEM) and sodium p-chloromercuriphenyl sulphonate (PCMS) also inhibited prostaglandin inactivation by guinea-pig isolated lungs.7 All four compounds inhibited prostaglandin metabolism by a crude enzyme preparation from guinea-pig lungs.