Biosynthesis, secretion, and immunocytochemistry of trypsin modulating oostatic factor of Aedes aegypti

Trypsin modulating oostatic factor (TMOF) was followed by RIA in the ovary of female Aedes aegypti before and after the blood meal. The amount of TMOF in a pair of ovaries from females fed sugar for 3 days or blood for 24 h was low (1.7 ng). Between 24 and 48 h after the blood meal the amount of TMOF in the ovaries rapidly increased and reached a peak of 104 ng at 48 h. The amount of TMOF in the head of a female A. aegypti was very low (0.05 to 0.1 ng) during sugar and blood feeding. Immunocytochemical methodology identified the follicular epithelium as the site of biosynthesis of TMOF in the ovary. Females ovariectomized and fed a blood meal continued to synthesize trypsin for 64 h, whereas intact controls stopped at 40 h, indicating that a factor from the ovary regulates trypsin biosynthesis. Ovaries incubated in vitro with [3H]proline synthesized [pro-3H]TMOF that was identified by HPLC and by anti-TMOF serum. The ovary started to synthesize TMOF in vitro 24 h after the blood meal, and the synthesis reached a peak at 36 h and then declined. The synthesis of TMOF by the ovary is closely correlated with the termination of trypsin biosynthesis in the female mosquito's midgut. Ovaries that were pulsed with [3H]proline for 30 min synthesized [pro-3H]TMOF which was chased into the medium with unlabeled proline, indicating that the hormone is secreted by the ovary. These results indicate that TMOF is a secretory peptide, synthesized by the ovarian follicular epithelium and that it modulates trypsin biosynthesis in the mosquito's gut. © 1994 Wiley-Liss, Inc.