Use of dialysis fibers for the study of aerobic cells

The suitability of a perifusion system for the study of renal tubules trapped in different types of dialysis fibers has been investigated. First, the equilibration times across the fiber membranes were estimated by following the penetration of the dysprosium tripolyphosphate shift reagent inside the fibers using 23Na nuclear magnetic resonance. These times ranged from less than 1 min for microfibers to 30 min for some large diameter fibers. When cortical tubules were introduced into cuprophan dialysis microfibers (200 microns internal diameter) and perifused by rapid recirculation of cell culture medium, metabolic viability, as determined by a linear glucose and ammonia production from glutamine and lactate, was found to exceed 10 (dog) or 3 h (rat), an unprecedented time period for such structures. As evidenced by the sensitivity to furosemide, the lumen of thick ascending limb tubules was kept open by including 50 mM mannitol in the perifusate. Fibers with large internal diameters (1100 microns) were found to be less suitable owing to the slow equilibration rates with the intrafiber compartment. All types of fibers showed minimal line-broadening effects on the 31P nuclear magnetic resonance signals.