Effect of nitric oxide on ammoniagenesis in rats

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 m M L-glutamine at 37 degrees C and glutamine-stimulated ammoniagenesis which was further elevated with 10(-7) M ANGII showed a time-dependent decrease during 2 h. 10(-4) M L-NAME or 10(-5) M L canavanin caused a similar ammonia elevation to that of ANGII, whereas the addition of 10-5 M 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. Copyright (c) 2006 S. Karger AG, Basel