Partial purification of a novel insect antidiuretic factor from the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera : Chrysomelidae), which acts on Malpighian tubules

In this study, we report for the first time the presence of an antidiuretic factor in the head of the Colorado potato beetle (Leptinotarsa decemlineat a (Say)) which acts directly on Malpighian tubules. Biologically active fra ctions were isolated from the head and separated using molecular weight fil tration and high-performance liquid chromatography (HPLC). The resulting fr actions were tested for their antidiuretic activity on single isolated Malp ighian tubules. Antidiuretic activity was found in the 25% acetonitrile Sep -Pak fraction and the Cn-2 (3000-10,000 MW) and Cn-3 (<3000 MW) fractions, suggesting that the antidiuretic factor was probably a peptide of 25 to 50 amino acids. The antidiuretic factor was very potent, since after five succ essive fractionations on two different HPLC columns, a high level of inhibi tion (63%) of fluid secretion by Malpighian tubules could be observed at lo w dose (0.14 head-equivalent/<mu>l). The antidiuretic factor isolated from the head of the Colorado potato beetle was not affected by repeated freezin g and thawing but was sensitive to heat. The differences observed between t he Colorado potato beetle antidiuretic factor and other insect diuretic and antidiuretic factors may indicate the possibility of a novel family of wat er regulation hormones in insects. Crown Copyright (C) 2001 Published by El sevier Science Ltd. All rights reserved.