title: [Partial characterization of esterase activity in a temephos-resistant Aedes aegypti strain].
abstract: BACKGROUND
  the esterase enzymes have been defined as the mechanism of resistance to temephos in Aeges aegypti in Cuba, which is the most used larvacide worldwide.
  
  
  OBJECTIVE
  to partially characterize the activity of esterases in exposed and nonexposed larvae at sublethal doses of temephos in an Aedes aegypti strain that is resistant to this product.
  
  
  METHODS
  a susceptible reference Aedes aegypti strain (Rockefeller) and another temephos-resistant strain (SANtemFII) were used. The larvae from SANtemF11 strain were exposed to lethal concentration 90 (LC90) of temephos (1 ppm); 10 % of the surviving larvae after 24 hours (SANtem[24 h] was moved to clean water, with no exposure to insecticide for 24 hours (SANtem [48 h]). The activity of esterases was partially characterized in these larvae through biochemical assays and gel-polyacrylamide electrophoresis. The molecular weight of esterase A 4 (ESt. A4) was estimated with the support of sodium duodecyl sulophate (SDS-PAGE).
  
  
  RESULTS
  the activity of esterases in SANtemF11 was significantly higher than in Rockefeller strain. Significant reduction of the activity of esterases in surviving larvae was observed (SANtemF11 [24 h], but it increased 24 h later without exposure to temephos. The zymogram showed that 10% of larvae that survived from temephos action, just the esterase A4 band increased if compared with those of SAntemF11. The estimated molecular weight of esterase A4 was 58 kDa.
  
  
  CONCLUSIONS
  the presence of a specific band of esterase (58 kDa) in surviving larvae confirmed the role of these enzymes in insecticidal resistance. The diagnosis of the function of the esterases in resistance to temephos through biochemical tests should not be made in larvae exposed to sublethal doses of this insecticide, in order to avoid false negatives.
authors: Instituto de Medicina Tropical "Pedro Kourí", La Habana, Cuba. mrodriguez@ipk.sld.cu
authors: C María Magdalena
authors: CM
authors: Rodríguez
authors: C Juan A
authors: CJ
authors: Bisset
authors: C Hilda
authors: CH
authors: Hernández
authors: Yanelys
authors: Y
authors: Ricardo
authors: Leidys
authors: L
authors: French
authors: Omayda
authors: O
authors: Pérez
authors: Ilario
authors: I
authors: Fuentes
mesh_terms: D000330:Aedes / Q000201:enzymology*; D000818:Animals; D004950:Esterases / Q000502:physiology*; D007305:Insecticide Resistance / Q000502:physiology; D007306:Insecticides; D000002:Temefos
chemical_list: D007306:Insecticides; D004950:Esterases; D000002:Temefos