Fat body involvement in the plasma vitellogenin changes during recovery phase in Rana esculenta

The role of fat body in the reproductive physiology of Rana esculenta was investigated during recovery phase. Changes in the ovarian weight, plasma vitellogenin (VTG) and estradiol-17-beta-levels were analyzed in intact frogs, in those without fat bodies (FBD) and in males and females injected with estradiol-17-beta. The ovarian weight decreased by day 28 in intact females but not in FBD animals. At the same time plasma VTG titers sharply decreased on day 21 in intact animals, but no significant changes were found in FBD females. Male frogs never synthetize VTG; they do so, however, after injection of estradiol-17-beta, FBD males showed higher VTG titers than intact males. The results obtained in vitro showed a sharp decrease of vitellogenin added in the medium of cultured fat body. Thus, the in vivo and in vitro results allow us to suggest that fat bodies metabolize plasma vitellogenin, at least during recovery phase; therefore ovarian growth may depend on an interplay among hepatic vitellogenin synthesis, fat body metabolic activity and ovarian uptake.