Differences in pattern visual evoked potential (PVEP) between hemodialysis and peritoneal dialysis patients.

The visual evoked potential was recorded in peritoneal and hemodialysis patients as compared to normal controls. By using the appropriate visual stimulus we were able to disclose specific VEP abnormalities for each of the two dialysis groups. The dissociation found between the latency of N70 and P100 in peritoneal dialysis patients suggests a possible postsynaptic visual abnormality not described previously. The correlation between the high serum aluminum and the P100 latency of peritoneal dialysis patients requires further investigation.

Evidence for the transport function of uricase, an oxidative enzyme.

[2-14C]urate uptake was examined in proteoliposomes prepared with phosphatidylcholine and either pig liver uricase or albumin, and in protein-free liposomes. Urate uptake was only evident in proteoliposomes that contained active uricase. Uptakes were indistinguishable in the presence and absence of inwardly directed gradients of sodium, potassium, or choline chloride or outwardly directed hydroxyl gradients. Both urate and allantoin accumulated within proteoliposomes during urate uptake; however, [2-14C]allantoin was not taken up by proteoliposomes. Urate uptake was accelerated in the presence of unlabeled urate in the trans position, saturable, and competitively inhibited by oxonate, findings consistent with carrier-mediated transport. Finally, the kinetics of urate uptake and oxidation were virtually identical, implying that the transporter is uricase. Thus, these studies provide evidence that uricase can function as a transport protein for urate when inserted in a lipid bilayer: transport via uricase is neither cation dependent (not a cotransporter) nor dependent on an exchangeable anion (not a urate/anion exchanger). Additionally, these studies demonstrate that neither urate nor allantoin cross lipid bilayers by simple or nonionic diffusion.