AJP - Regulatory, Integrative and Comparative Physiology, Vol 250, Issue 3 328-R332, Copyright © 1986 by American Physiological Society
Peptide nature of two mosquito natriuretic factors
D. H. Petzel, H. H. Hagedorn and K. W. Beyenbach
High-pressure liquid chromatography (HPLC) of saline extracts of Aedes
aegypti heads yields three fractions (from a total of 108) that affect
transepithelial voltage and/or fluid secretion in isolated Aedes Malpighian
tubules. In this study we investigated the physical and chemical nature of
the active materials in these fractions. Gel-filtration chromatography
revealed that the molecular weights of the three fractions were between
1,900 and 2,700. To test their thermostability the fractions were
repeatedly frozen and thawed over a period of 110 days without loss of
biological activity. Boiling at 100 degrees C for 5 min failed to
significantly reduce their biological effects in isolated Malpighian
tubules. In contrast, treatment with the proteolytic enzyme mixture,
pronase, destroyed activity in all three. Fraction I no longer depolarized
the transepithelial voltage of in vitro perfused Malpighian tubules, and
fractions II and III completely lost their ability to stimulate fluid
secretion and to affect transepithelial voltage. We conclude that our HPLC
isolation yields a heterogeneous group of three polar low-molecular weight
peptides. Expression of their biological activities in Malpighian tubules
depends on intact peptide bonds.
