BIOSYNTHESIS OF HYDROCARBONS AND CONTACT SEX-PHEROMONE AND THEIR TRANSPORT BY LIPOPHORIN IN FEMALES OF THE GERMAN-COCKROACH (BLATTELLA-GERMANICA)

The sites of synthesis, and transport of hydrocarbons and methyl keton e contact sex pheromone, were examined in the German cockroach. The ab dominal integument of 7-day old Blattella germanica females showed lin ear incorporation of [1-C-14]propionate into hydrocarbon and pheromone for at least 4 h in vitro, whereas other body parts including the hea d, wings, legs, thorax, fat body, digestive tract, and vitellogenic ov aries produced negligible amounts of hydrocarbon and pheromone. The st ernites synthesized significantly more hydrocarbon and methyl ketones than the tergites, and in both, the incorporation of propionate into h ydrocarbon correlated well with its incorporation into the methyl keto ne pheromone, suggesting that the abdominal oenocytes or epidermal cel ls synthesize both hydrocarbon and pheromone. The abdomen contained ab out 55% of the total hydrocarbon and pheromone in the female, and both were located mainly in the ovaries, integumental epidermal cells (inc luding oenocytes), fat body, and hemolymph. Hemolymph contained up to 20% of the internal hydrocarbons and their methyl ketone derivatives, suggesting that hemolymph carries and circulates hydrocarbon and phero mone in the female. A high density lipophorin (1.109 +/- 0.002 g/ml) w as isolated and purified from hemolymph by KBr gradient ultracentrifug ation and was shown to be the only hemolymph protein that carries hydr ocarbon and pheromone. This result suggests that lipophorin loads newl y synthesized hydrocarbon and pheromone from the abdominal epidermis a nd transports them to various tissues, including the ovaries, fat body and possibly the epicuticle. After injection of radiolabeled propiona te, newly synthesized radiolabeled methyl-branched hydrocarbons appear ed first in the epidermal fraction (with oenocytes) and hemolymph, and later on the epicuticle. When veins entering the fore-wings were cut so that hemolymph circulation to the wings was blocked, the amount of newly synthesized hydrocarbon on the wings was significantly lower tha n on intact fore-wings. Significantly more radiolabeled hydrocarbon wh ich had been topically applied on the sternites was recovered in the h emolymph than on the surface of the wings. These results show that tra nsport of hydrocarbon is mediated by lipophorin, which shuttles newly synthesized hydrocarbon and methyl ketone sex pheromone from the abdom inal oenocytes to epicuticular and internal deposition sites, includin g the ovaries.