Relationship between partial inhibition of glycolysis and hemolysis after induction of gametocytogenesis in synchronous cultures of Plasmodium falciparum

In the present study, the low molecular-weight fraction of the culture supernatant of anti-Plasmodium falciparum antibody-producing hybridoma cells (HybSL) was used in synchronous culture with P. falciparum FVO strain. When synchronous cultures were treated with HybSL solution on day 5, gametocytogenesis was also induced. Gametocytes were consistently found from the third day after treatment and reached a peak on the fourth day. An increase in pH and hemoglobin concentrations and decrease in lactate concentrations were observed on the first day after treatment. These phenomena suggested that HybSL solution partially inhibited glycolysis of erythrocytes parasitized with schizonts and resulted in hemolysis of infected erythrocytes. On the other hand, the production of gametocytes did not increase in cultures treated with HybSL solution on day 4 of synchronous cultures in which ring forms were plentiful. Most ring forms were not killed by HybSL solution and quickly developed to trophozoites and schizonts rather than gametocytes. Consequently, it is assumed that ring forms on day 4 of synchronous cultures have finished differentiation into the asexual stage. The conversion of asexual parasites to gametocytes may be triggered only when late-stage trophozoites or early-stage schizonts are treated with HybSL solution.