Inhibition of blood digestion and oocyte growth in Aedes aegypti by 5-fluorouracil.

Abstract

1. Oviposition in Aedes aegypti females is inhibited by 5-fluorouracil (FU); 0.01% FU fed in the blood meal causes about 99% inhibition of oviposition. The inhibition of oviposition by FU is temporary; some of the females which laid no eggs after their first blood meal recover their ability to oviposit after a second blood meal. The eggs laid by the FU-treated females hatch normally.2. Oviposition in mosquitoes is also inhibited by feeding FU in sugar solution before the blood meal; 0.05% causes about 95% inhibition of oviposition when given in sugar solution for two days. This effect is also temporary. The eggs laid by females treated with FU in sugar solution batch normally even when both sexes have been treated.3. FU slows down the growth of oocytes; the treated females oviposit later than the controls. The rate of oocyte growth and the percentage of females developing mature eggs is proportional to the amount of FU.4. Blood digestion is retarded by FU-treatment. The delay in blood digestion is already evident one day after feeeding by the color of the blood mass. The period of blood digestion in females treated with 0.05% FU in sugar solution is more than twice that in the controls.5. Midgut proteolytic activity is inhibited in FU-treated females. The extent of inhibition is proportional to the amount of FU and the time interval between FU-treatment and the blood meal.6. FU does not inactivate protease in vitro.7. A close correlation between the stage of ovarian development and the amount of midgut protease has been found.8. Soy bean trypsin inhibitor, which inactivates mosquito protease in vitro, also retarded the maturation of eggs in vivo.9. The effect of FU on oocyte maturation in mosquitoes could be an indirect effect (oocyte growth is inhibited because of a lack of midgut protease) or a direct effect of FU on the synthesis of specific proteins in all parts of the insect body.