Synthesis of vitellogenin by the follicle cells of Rhodnius prolixus

The synthesis and secretion of vitellogenin by the ovary of Rhodnius prolix us was investigated. Using whole ovary or epithelial cells isolated from fo llicles of different sizes, it is shown that the follicle cells are a site of synthesis for this protein in the ovary. The ovaries or follicle cells w ere incubated in vitro with [S-35]-methionine or (32)Pi and the secretion o f newly synthesized ovarian vitellogenin (O-Vg) was estimated by the radioa ctivity associated with the immunoprecipitate or acid-precipitate proteins in the culture medium. The radioactive O-Vg was analyzed by SDS-PAGE follow ed by autoradiography or after elution from a DEAEToyopearl column. The pre sence of O-Vg inside the follicle cells was detected by immunofluorescence and immunogold labels. Both methods revealed strong labeling inside the fol licle cells. While the capacity for total protein synthesis by the follicle cells was maximal during the early phase of vitellogenesis (in small folli cles), the synthesis of O-Vg reached its peak during the late phase of oocy te growth, just before formation of the chorion. A possible role for ovaria n vitellogenin in Rhodnius and its relationship with Vg synthesis by the fa t body is discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.