Some factors inducing formation of metacyclic stages of Trypanosoma cruzi.

Epimastigotes of Trypanosoma cruzi, Peru strain, incubated in Contreras' artificial triatomine urine transformed into metacyclic trypomastigotes within 48 h at 28 degrees C when 10 mM L-proline or L-glutamate was added to the medium. Smaller numbers of metacyclic stages were induced in the presence of glucose or L-alanine. The L-leucine and L-isoleucine, 2 amino acids known to inhibit proline catabolism, inhibited proline-induced metacyclogenesis. Cells gassed with 5% CO2 showed significantly faster rates and higher levels of transformation than those not gassed, therefore indicating the additional importance of CO2 for transformation.