Histamine and esterases in the salivary gland of the mosquito, Culex pipiens pallens

Abstract

In an attempt to elucidate the mechanism of skin-reactions to mosquito bites, components in the salivary gland of mosquitoes were studied. Crude extract and lower molecular weight fraction (mol. wt. <6,000) of the salivary gland extract of Culex pipiens pallens showed extravasation activity in the skin of guinea pigs not sensitized previously. But higher molecular weight fraction (mol. wt. >6,000) of the extract did not have the extravasation activity. By the o-phthalaldehyde staining method, histamine was detected in the whole salivary glands of Cx. pipiens pallens soon after their emergence, and the reaction intensity increased when they were mature; in Aedes togoi, the proximal portion of the lateral lobe of the salivary gland reacted strongly. By the azo dye staining method, using α- and β-naphthyl acetate, strong esterase activity was found in the whole salivary gland of Cx. pipiens pallens; in Ae. togoi and Ae. albopictus, only the proximal portions of the salivary glands reacted to some extent. In vitro tests with the salivary gland extract of Cx. pipiens pallens did not exhibit hydrolytic activity on TAME, BTEE and ATEE, and neither anticoagulating activity nor hemolytic activity was observed. Histamine, putrescine, spermine, and spermidine, but not serotonin, were detected in the salivary gland extract by ion-exchange high performance liquid chromatography. Histamine contained in the female body was mainly found in the salivary gland and head.