SCIENTIFIC THINKING Mercury is known to inhibit the permeability of water channels. To help establish that the protein isolated by Agre’s group was a water channel (see Module 5.7), the researchers incubated groups of RNA-injected oocytes (which thus made aquaporin proteins) in four different solutions: plain buffer, low concentration and high concentration of a mercury chloride (HgCl2) solution, and low concentration of a mercury solution followed by an agent (ME) known to reverse the effects of mercury. The water permeability of the cells was determined by the rate of their osmotic swelling. Interpret the results of this experiment, which are presented in the graph below.
Data from G. M. Preston et al., Appearance of water channels in Xenopus oocytes expressing red cell CHIP28 protein, Science 256: 3385–7 (1992).
Control oocytes not injected with aquaporin RNA were also incubated with buffer and the two concentrations of mercury. Predict what the results of these treatments would be.
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CAMPBEL BIOLOGY:CONCEPTS & CONNECTIONS
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