Fig. 5. Inhibition of clathrin-mediated endocytosis negatively regulates oocyte maturation. (A) Membrane capacitance [Cm(nF)] of control Xenopus oocytes and oocytes injected with C3 exoenzyme (1 ng/oocyte) 2 hours earlier. (B) GVBD timecourse from a representative experiment after C3 exoenzyme injection. Cells were injected with C3 exoenzyme 1 hour before progesterone treatment or left untreated. The histograms indicate percent GVBD and normalized time to GVBD₅₀ (mean±s.e.; n=3). GVBD levels are those reached at the end of the experiment, typically no longer than 18 hours. (C) Transferrin endocytosis assay. Examples of confocal cross-sectional images through oocytes used to quantify Alexa-633-labeled transferrin internalization after overnight incubation with either the carrier control DMSO or 332 µM MDC. The number of labeled vesicular structures and their equivalent sphere volumes were quantified, as detailed in Materials and methods. (D) Membrane capacitance of oocytes incubated in the DMSO carrier control and oocytes treated with 332 µM monodansyl cadaverine (MDC) overnight. (E) GVBD time course from a representative experiment after MDC treatment. Cells were incubated with MDC overnight or left untreated before progesterone treatment. The histograms indicate percent GVBD and normalized time to GVBD₅₀ (mean±s.e.; n=5). Scale bar: 100 µm. Con, control oocytes.