Comparative histochemical investigation of the organ of Corti in the kangaroo rat, gerbil, and guinea pig.

Abstract

AbstractThe distribution of carbohydrates, proteins, and lipids was studied in the cochleae of kangaroo rat, gerbil, and guinea pig using both fixed paraffin sections and fresh‐frozen cryostat sections. Enzyme distribution in the cochleae of the three speices was studied with both EDTA‐decalcified and undecalcified fresh‐frozen cryostat sections.Although the cochleae of the three species are morphologically different, their distributions of proteins, carbohydrates, and lipids are similar. The zona pectinata of the basilar membrane—which is hypertrophied in the kangaroo rat and gerbil but normal in the guinea pig—stains the same in all three species. The unique, flaskshaped Hensen cells of the kangaroo rat contain more protein than do the normal Hensen cells of the gerbil and guinea pig. At least some of the protein in the kangaroo rat Hensen cells is in the form of carboxylic esterases which are not affected by 10−4 M eserine, but are inhibited by 10−2 M eserine and 10−6 M E600. More than one population of carboxylic esterases is indicated by this reaction to inhibitors and by the results of enzyme distribution tests which used different substrates. A high concentration of malate dehydrogenase in the kangaroo rat Hensen cells may be related to the synthesis of carboxylic esterases. The possible role of these esterases in cochlear functioning is discussed.