Schistosoma mansoni: effect of recombinant tumor necrosis factor alpha on fecundity and [14C]-tyrosine uptake in females maintained in vitro.

It has been reported that recombinant tumor necrosis factor alpha (rTNF alpha) stimulates egg-laying in Schistosoma mansoni females. Because tyrosine requirement is increased in female undergoing sexual maturation in preparation for oogenesis and tyrosine is a major component of eggshell protein, we wanted to determine whether females treated with rTNF alpha would also incorporate more tyrosine. Adult females were first treated with 10, 20 or 40 ng/ml rTNF alpha for 1, 3 or 6 hr in RPMI 1640 containing 10% fetal calf serum (FCS). Another two groups of females were each exposed either to males or to male excretory-secretory (ES) products for 1 hr. They were then exposed to 20 microCi/ml-1 [14C]-tyrosine for 1 hr in RPMI 1640 containing 10% FCS. All females were incubated individually unless indicated otherwise. Females incorporated more tyrosine after exposure to males or their ES products. They incorporated significantly more tyrosine when treated with rTNF alpha for 1 hr; the increased uptake correlated with increasing amounts of rTNF alpha used. Although after a 3-hr treatment with 10 ng/ml rTNF alpha females incorporated slightly more tyrosine than controls, increasing amounts of rTNF alpha had an adverse effect. Females treated with rTNF alpha for 6 hr incorporated less tyrosine than controls and those treated for 1 hr. SDS-PAGE and fluorography did not reveal any differences in polypeptide profiles of untreated and rTNF alpha-treated females. These unexpected results led us to study the effect of rTNF alpha on fecundity in females. Contrary to the published report, we observed a sharp decline in egg-laying in females when exposed to increasing concentrations of rTNF alpha in vitro.