The synthesis of hemolymph proteins by the larval midgut of an insect Calpodes ethlius (Lepidoptera:Hesperiidae) |
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Institution: | 1. Department of Veterinary Paraclinical Sciences, College of Veterinary Medicine, University of the Philippines Los Baños, Los Baños, Laguna 4031, Philippines;2. Laboratory of Infectious Diseases, Joint Faculty of Veterinary Medicine, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan;3. Laboratory of Parasitology, Joint Faculty of Veterinary Medicine, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan;4. National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada-cho, Obihiro, Hokkaido 080-8555, Japan;5. National Agricultural and Food Research Organization, Tsukuba, Ibaraki 305-0856, Japan |
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Abstract: | Ligated tubes of Calpodes ethlius (Lepidoptera:Hesperiidae) larval midgut with normal (i.e. apical secretions into the lumen and basal into the hemocel or medium) or inverted orientation (i.e. apical secretions into the hemocoel or medium and basal into the lumen) were incubated in artificial hemolymph in the presence of 35S]methionine to investigate protein synthesis and vectorial secretion. The midgut synthesizes and secretes at least eight polypeptides basally and seven apically. The tissue also synthesizes many other polypeptides that are not released at either surface. Two dimensional analysis of proteins labeled in vitro and in vivo showed that (a) proteins synthesized in vitro are the same as those synthesized in vivo, (b) different proteins are secreted on apical and basal surfaces, (c) in vitro apical secretions are the same as in vivo luminal proteins, (d) at least two of the basal secretions can be demonstrated in the hemolymph labeled in vivo. Almost all basal secretions showed immunological similarity with hemolymph proteins as observed by immunoprecipitation and fluorography. Arylphorin is a main hemolymph protein synthesized by the midgut. Midgut arylphorin has been identified by its precipitation by antibodies to hemolymph arylphorin. We conclude that insect midgut has bi-directional secretion. Luminal proteins (presumably digestive enzymes and perhaps goblet cell luminal contents) are carried to the apical face. A different set of proteins are carried basally to the hemolymph. |
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