Lipophorin of female Blattella germanica (L.): characterization and relation to hemolymph titers of juvenile hormone and hydrocarbons

High density lipophorin (HDLp) from the hemolymph of the German cockroach, Blattella germanica (L.) (Family Blattellidae), has an apparent molecular w eight of 670 kDa, with an isoelectric point of 7.0 and a density of 1.109 8 /ml. It is composed of two subunits, apolipoprotein-I (212 kDa) and apolipo protein-II (80 kDa), and consists of 51.4% lipid, 46.2% protein and 2.4% ca rbohydrate. Hydrocarbons constitute 42.2% of the total lipids which also co ntain diacylglycerol, cholesterol and phospholipid. Lipophorin is rich in t he amino acids glutamic acid, aspartic acid, lysine, valine, and leucine. S pecificity of a polyclonal antibody was demonstrated by Western blotting an d Ouchterlony immunodiffusion: the antiserum recognized native HDLp and apo lipoprotein-I, but not apolipoprotein-II, purified vitellin, or other hemol ymph proteins. It also recognized a protein in the hemolymph of Supella lon gipalpa (Blattellidae) but did not cross-react with hemolymph proteins from Periplaneta americana (Blattidae) or Diploptera punctata (Blaberidae). An enzyme-linked immunosorbent assay was developed to measure the HDLp titer i n the hemolymph of adult females. The titer of HDLp, a juvenile hormone bin ding protein, exhibited no clear relationship to the changing titer of juve nile hormone in hemolymph. The hemolymph titer of hydrocarbon, which is als o carried by HDLp, showed some functional relation to the concentration of HDLp in the hemolymph. Because it-concurrently serves multiple functions in insect development and reproduction, lipophorin titer might covary with th e titers of lipid ligands that occur at high concentrations and require ext ensive shuttling through the hemolymph. (C) 1999 Elsevier Science Ltd. All rights reserved.