Oenocytes of the cricket, Gryllus bimaculatus,
were characterized by a continuously high secretion of ecdysteroids over
several hours. A factor extracted from heads of the male adults caused
the oenocytes to enhance immunoreactive ecdysteroid secretion in vitro.
This factor was isolated by high performance size exclusion chromatography.
Its molecular weight ranged from 26.5 to 30.0 kDa. The partially purified
bioactive substance stimulates the ecdysteroid synthesis of oenocytes
in a time-and dose-dependent manner. The ecdysiotropin was susceptible
to protease degradation and furthermore showed resistance to boiling and
alkylation. Exopeptidase did not affect the activity of the peptidergic
factor, suggesting that N- and C-terminus are protected. Treatments with
dithiothreitol and neuraminidase suggest that disulfide bridge and carbohydrates
are necessary for the biological activity of the oenocyte-stimulating
ecdysiotropic factor. This study is the first evidence that a factor of
head adult insect increased in vitro ecdysteroid secretion in oenocytes
that are epidermal in origin.