Phenylthiourea, an Effective Inhibitor of the Insect Haemolymph Melanization Reaction, Interferes with the Detection of Lipoprotein Hydroperoxide

Abstract

Phenylthiourea (PTU) is an effective inhibitor of insect haemolymph melanization. PTU or thiourea, however, took a hydroxide moiety from cumene hydroperoxide and peroxidated egg yolk low density lipoprotein (LDL) from chicken. Oxygenized forms of the chemicals, phenylurea and urea, did not have such an effect. A conjugated diene structure of the LDL was not affected by incubation with PTU. Thus, the effect of PTU seems to be specific to the hydroperoxide moiety. The significance of the interaction between hydroperoxide and PTU is discussed with special reference to the bleeding technique and physiology of insect haemolymph.