IP Endocrinology

A factor from the cricket testis that inhibits ovarian exdysteroid biosynthesis

M.W. Lorenz 1 , J.I. Lorenz 1 , K. Seifert 2 & K.H. Hoffmann 1

1 Dept. of Animal Ecology 1 and 2 Dept. of Organic Chemistry I/2, Univ. of Bayreuth, 95440 Bayreuth, Germany

Ecdysteroids and juvenile hormones play a central role in the regulation of insect development and reproduction. In the larval stages they control moulting and metamorphosis whereas, in the adult insect, they regulate the biosynthesis of yolk proteins in females and spermatogenesis and growth of the accessory reproductive glands in males. Only very few factors that regulate ecdysteroid biosynthesis have been identified from animal tissues, all of them being peptides: two ecdysiotropins, the prothoracicotropic hormone from the silkworm Bombyx mori and the testis ecdysiotropin from the gypsy moth Lymantria dispar as well as two ecdysiostatins, trypsin-modulating oostatic factor from Neobellieria bullata and Calliphora vicina, and the W 2 W 9 amide peptide family (type B allatostatins) from Gryllus bimaculatus. Our screening for factors that regulate juvenile hormone and ecdysteroid biosynthesis in the Mediterranean field cricket, G. bimaculatus, led to the finding that the testes of adult males contain an extractable factor that inhibits ovarian ecdysteroid biosynthesis in females. Crude acidic methanol extracts from testes, dissected from 4-6 day-old adult males, were prepurified by C18 Seppak fractionation using a stepwise gradient of acetonitrile in water, containing 0.1% trifluoroacetic acid. The 16% acetonitrile fraction showed marked ecdysiostatic activity when tested on ovaries of 4 day-old adult females and was subjected to further purification by high-performance liquid chromatography. Upon a three-step purification using C8 and C18 reversed-phase columns and water/acetonitrile gradients with pentafluoropropionic acid and heptafluorobutyric acid, respectively, as ion-pairing reagents in the first two steps, and no ion-pairing reagent in the third step, a single uv-absorbance peak was obtained. Analysis by gas chromatography-mass spectrometry revealed that this peak contained indole-2-carboxylic acid (I2C) as the major component (ca. 50%), along with lauric, myristic and palmitic acid. Tests with the synthetic compounds identified I2C as an ecdysiostatic factor, acting in a dose-dependent manner with 50% inhibition of ecdysteroid biosynthesis at 10 -6 -10 -5 M I2C and a maximum inhibition of 60-70% at 10 -4 -10 -3 M I2C. No effect of I2C on juvenile hormone biosynthesis by corpora allata from 5 day-old adult females could be observed, even at the highest concentration (10 -4 M) tested. The role of I2C in the regulation of development

Copyright: The copyrights of this original work belong to the authors (see right-most box in title table). This abstract appeared in Session 18 – REPRODUCTION AND DEVELOPMENT Symposium and Poster Session, ABSTRACT BOOK II – XXI-International Congress of Entomology, Brazil, August 20-26, 2000 and in 14th Ecdysone Workshop (2000), Rapperswil, Switzerland, Abstract Book, page 27 (Lorenz, J.I., Lorenz, M.W., Seifert, K., Hoffmann, K.H.: Ecdysiostatic factors isolated from the cricket, Gryllus bimaculatus) .