Correlation of glutathione S-transferase and DDT dehydrochlorinase activities with DDT susceptibility in Anopheles and Culex mosquitos from northern Thailand.

Comparative DDT-susceptibility status as well as glutathione S-transferase activity and DDTase activity of Anopheles minimus (A). An. annularis and Culex quinquefasciatus were investigated to ascertain the role of these enzymes in DDT-resistance. The standard WHO susceptibility test kits was used to discriminate between resistant and susceptible populations. GST activity was measured in microtiter plates whereas DDTase activity was determined by HPLC quantitation of DDT metabolites. This is the first report of DDT-resistance in the Thai malaria vector, An. minimus species A. A positive correlation of DDT-resistance and DDTase activity was observed in this species as well as in the suspected vector, An. annularis. However, GST activity was not correlated to DDT-resistance in either species. Statistical analysis and scatter plots demonstrated the non-correlation between DDTase and GST activity in An. annularis. Studies in Culex quinquefisciatus revealed difference in GST/ DDTase and the relationship to DDT-resistance compared to the anopheline species. The Culex GST activity is correlated to DDTase activity. These results suggested that a positive correlation of GST and DDTase activity might be species dependent.

The effect of oral contraceptives on protein metabolism.

The effect on protein and amino acid metabolism of combined oral contraceptives (OC) containing 150 micrograms of laevonorgestrel and 30 micrograms of ethinyl oestradiol was studied in a group of 34 healthy non-lactating women. This was compared to an identical study conducted in another group of 19 subjects who used IUCDs for contraception, and also in two other groups of subjects who were given an additional multivitamin preparation on a daily basis (29 subjects) and on the days when OC was not taken (29 subjects). Assessments were made prior to, and during the third week of the 4th, 7th, and the 13th cycles of OC treatment. Results indicated that the ceruloplasmin and retinol binding protein underwent significant increases with OC usage, while sex hormone binding globulin concentration, on the other hand, remained unaffected. At the same time, a significant reduction of several of the plasma amino acid and plasma albumin concentrations was observed, suggesting that the increase in the visceral and other types of protein concentrations previously noted was due to increased hepatic protein synthesis rather than increased breakdown or excretion as result of OC intake. Interesting biochemical alterations and metabolic effects previously observed may well be related to this altered synthesis and release of proteins and/or protein binders as well as induction of certain metabolic enzymes from the liver.