Schistosoma mansoni: females enhance [14C]-tyrosine incorporation in males maintained in vitro.

Incorporation of radiolabelled tyrosine was examined in males of Schistosoma mansoni maintained in vitro. Adult worms were recovered from mice and only those that were paired were used. Males and females were separated and placed in 4 degrees C RPMI 1640 containing 10% fetal calf serum (FCS). Individual males were incubated for 1 h either alone or with a female. Other males were incubated in a medium containing 40 ng ml-1 recombinant tumour necrosis factor alpha (rTNF alpha). Subsequently, males were incubated with or without females for 1 h in a medium containing 20 muCi ml-1 [14C]-tyrosine. All incubations were carried out in RPMI 1640 containing 10% FCS at 37 degrees C under 5% CO2. Untreated single males incorporated small amounts of labelled tyrosine. Pretreatment of single males with rTNF alpha did not affect their tyrosine incorporation (P = 0.693). However, males maintained in vitro with females incorporated 221% more tyrosine than the controls (P = 0.00008), suggesting that a chemical stimulus from the female affects tyrosine incorporation in males.