HYPERGLYCEMIC HORMONES INHIBIT PROTEIN AND MESSENGER-RNA SYNTHESIS ININ-VITRO-INCUBATED OVARIAN FRAGMENTS OF THE MARINE SHRIMP PENAEUS-SEMISULCATUS

The present work shows for the first time that peptides belonging to t he Crustacean hyperglycaemic hormone family (CHH-family hormones) from Penaeus japonicus affect protein and mRNA synthesis in in vitro-incub ated ovarian explant fragments removed from vitellogenic females of Pe naeus semisulcatus. Reduced levels of protein synthesis, determined by TCA-precipitable S-35-labeled proteins, were found in the presence of crude sinus gland extracts from both P. semisulcatus and P. japonicus . A similar inhibitory effect compared to controls was found with each of the seven CHH-family peptides. Non-CHH-family peptides did not red uce protein synthesis. Crude sinus gland extracts prepared from Il sem isulcatus were at least 20-fold more effective than sinus gland extrac ts of Il japonicus. The inhibition level was directly related to the c oncentration of the peptide in the incubation media, but its degree va ried among the different tested peptides. The profile of proteins synt hesized during in vitro incubation was analyzed using polyacrylamide g el electrophoresis under denatured and reduced conditions (SDS-PAGE), followed by autoradiography. Synthesis of several proteins was reduced , including proteins with electrophoretic mobility similar to that of vitellin. Immunoprecipitation with antiserum prepared against native o varian vitellin confirmed the inhibitory effect of CHH-family peptides on vitellin synthesis. The crude sinus gland extract and CHH-family p eptides also inhibited RNA synthesis, as determined by [H-3]uridine in corporation into mRNA of ovarian fragments. It is concluded that in ad dition to their role in carbohydrate metabolism, CHH-family peptides m ay also influence ovarian physiology in crustaceans. (C) 1998 Academic Press.