Fig. 2. (A) Osmotic water permeability (P_f), (B) apparent glycerol permeability () and (C) urea uptake of Xenopus oocytes expressing sbAQP. Oocytes were injected with 50 nl of water containing 10 ng cRNA of sbAQP or 50 nl of distilled water only (control oocytes) 48 h prior to the experiments. P_f and were calculated from the time course of osmotic swelling of the oocyte in a hyposmotic- or glycerol-containing medium and urea transport activity was measured by [¹⁴C]urea uptake. Values are means ± S.E.M. of 10 oocytes from different batches. ME, mercaptoethanol.