An incubation system for the NMR study of kidney tubules

Isolated kidney cortical tubules require a very rapid oxygen supply and mechanical agitation to be optimally functional. A sample chamber in which a tubule suspension is oxygenated by recirculating oxygen gas inside a coil of dialysis fibers to avoid cell loss through bubbling and in which the tubules are agitated by a gas-driven turbine has been designed. In such a system, dog cortical tubules (35-45 mg/ml) were found to be metabolically stable for more than 3 h as indicated by linear lactate consumption and glucose production. Small pH variations resulting from carbon dioxide and bicarbonate productions were measured. Good-quality 23Na NMR spectra of dog kidney cortical tubules were recorded with such a system, allowing a 1-min time resolution.