Activity of insulin growth factors and shrimp neurosecretory organ extracts on a lepidopteran cell line

Ecdysteroids, or molting hormones, have been proven to be key differentiati on regulators for epidermal cells in the postembryonic development of arthr opods. Regulators of cell proliferation, however, remain largely unknown. T o date, no diffusible insect peptidic growth factors have been characterize d. Molecules structurally related to insulin have been discovered in insect s, as in other eucaryotes. We developed in vitro tests for the preliminary characterization of potential growth factors in arthropods by adapting the procedures designed to detect such factors in vertebrates to an insect cell line (IAL-PID2) established from imaginal discs of the Indian meal moth. W e verified the ability of these tests to measure the proliferation of IAL-P ID2 cells. We tested mammalian insulin and insulin-like growth factors (IGF -I, IGF-II). Following an arrest of cell proliferation by serum deprivation , IGF-I and IGF-II caused partial resumption of the cell cycle, evidenced b y DNA synthesis. In contrast, the addition of 20-hydroxyecdysone arrested t he proliferation of the IAL-PID2 cells. The cell line was then used in a te st for functional characterization of potential growth factors originating from the penaeid shrimp, Penaeus vannamei. Crude extracts of neurosecretory and nervous tissues, eyestalks, and ventral neural chain compensated for s erum deprivation and stimulated completion of mitosis. (C) 1997 Wiley-Liss, Inc.