STUDIES ON THE CHARACTERIZATION AND LOCALIZATION OF RAT PLACENTAL ESTERASES

Abstract

The nonspecific carboxylic esterases of the rat placenta were studied by electrophoretic, biochemical and histochemical methods, with naphthyl and naphthol AS esters as substrates. The enzymes were characterized by the effects upon their activity of a group of organophosphate inhibitors and of eserine, p-chloromercuribenzoate and urea solution. After electrophoresis at pH 7.5, zymograms show an extensive pattern of anodal and cathodal bands similar for both maternal and foetal portions of the placenta. The B (carboxyl) esterases are sensitive to inhibition with E600 and diisopropyl phosphorofluoridate at very low concentrations. The A (aryl) and C (acetyl) esterases undergo progressive inhibition at concentrations greater than 0.01 mM, and only one A esterase resists a 1.0 mM concentration. Mipafox resembles the other organophosphates in its effect on esterases only when it is used fresh. Comparison of the zymograms with the histochemical preparations permits the localization of some of the individual enzyme species separated by electrophoresis.