Effect of Nitric Oxide on Ammoniagenesis in Rats

Abstract

Aim: This in vitro study using rat cortical slices, isolated proximal tubules and mitochondria was conducted to investigate the effect of exogenous and endogenous nitric oxide on ammoniagenesis. Methods and Results: The cortical slices were incubated with phosphate-buffered saline containing 1 mML-glutamine at 37°C andglutamine-stimulated ammoniagenesis which was further elevated with 10^–7M ANGII showed a time-dependent decrease during 2 h. 10^–4M L-NAME or 10^–5ML-canavanin caused a similar ammonia elevation to that of ANGII, whereas the addition of 10^–5M SNAP attenuated the ammonia-increasing effects of ANGII and L-NAME. Basal or exogenous NO without significantly affecting glutamine uptake of the slices seemed to convert the glutamine deamidation pathway to transamination, since L-NAME increased the ammonia to glutamine ratio from 0.87 ± 0.08 mol/mol to 1.03 ± 0.04 (p < 0.01). L-NAME increased both ammoniagenesis and mitochondrial oxygen consumption but SNAP depressed them. Endogenous NO reduced ammoniagenesis without changing the mitochondrial permeability transition pore (PTP), whereas exogenous NO-induced attenuation in ammoniagenesis was associated with elevated PTP in a CsA-sensitive manner. Conclusion: These results demonstrated that in rat kidney, basal NO depresses mitochondrial oxygen consumption and attenuates ammoniagenesis without affecting PTP; however, exogenous NO inhibits ammonia production by disturbing PTP in isolated mitochondria.

The Effect of Heavy Muscle Activity on Renal Cytoresistance in Rats

“…As previously described, [40] renal proximal tubules were isolated from rats based on the method of Vinay et al [41] Briefly, the digested tissue was separated by centrifugation into four distinct bands, F1-F4. The proximal tubule-rich F4 band, after washing three times, was resuspended in krebs buffer and used for cholesterol determination or cytoresistance experiments.…”