Characterisation of the multixenobiotic resistance (MXR) mechanism in the freshwater snail Physa acuta from Patagonia (Argentina)

Figures & data

Figure 1 Measurement of MXR activity in Physa acuta snails from Patagonia tested within 24 h of collection. A, The accumulation of RB has been assessed in control snails and after inhibition with 30 µM verapamil at different concentrations of RB in the loading solution. Bars represent standard deviation of the mean (n = 7). The symbol (*) indicates a significant difference (P < 0.05) compared to the control. B, RB accumulation rate (verapamil/control) for the three tested concentrations of RB in the loading solution (n = 7). Bars with the same letter are not significantly different from each other. C, Efflux of RB was performed either in dechlorinated water or in 30 µM verapamil after a loading period of 4 h. Bars represent standard deviation of the mean (n = 4). Data are expressed in picomoles of accumulated/released RB per gramme of entire snail bodyweight.

Figure 2 Activity of the MXR system in snails after a 7 d period of laboratory depuration. A, Data represent the accumulated RB (picomoles per gramme of entire bodyweight) in control snails and after inhibition with 30 µM verapamil (n = 7) at the indicated treatment. B, Time course response for the activity of the MXR system after laboratory depuration. The accumulation of RB was determined following a period of 4, 7 and 15 d in snails exposed to clean water. The data are expressed as a percentage of the increase in RB accumulation in comparison to the control group measured immediately after collection, and are representative of those obtained in three other experiments. C, The accumulation of RB has been assessed in snails depurated without feeding or maintained in the presence of lettuce leaves for 7 d. RB accumulation was determined in the absence or presence of verapamil and data are expressed as percentage of control on collection day (P > 0.05, n = 5).

Figure 3 The activity of the MXR system in snails after a 7 d period of laboratory depuration. A, Efflux of RB assay was performed either in dechlorinated water or in 30 µM verapamil after a depuration period of 7 d. Bars represent standard deviation of the mean (n = 4). B, The MXR-related efflux rate of RB was determined in organisms tested on collection day and following laboratory depuration (7 d). Data represent the difference between the total efflux and the remaining efflux following verapamil inhibition for both conditions.

Figure 4 Detection of P-gp in Physa acuta snail homogenates. A, Western blot was probed with anti-P-gp C219 antibody which reacted with a diffuse band at c. 170 kDa and also at > 200 kDa (arrows). Vincristine-resistant K562 cell lysates were used as a positive control. Positions of molecular weight markers in kiloDaltons (kDa) are indicated on the left. B, Expression of c. 170 kDa band of P-gp was analysed on collection day and following a depuration period of 7 d. The relative level of P-gp using α-tubulin as the internal control is represented in the bar graph. Data represent mean ± SD from three separate experiments.