Role of nitric oxide in the early renal hemodynamic response after unilateral nephrectomy

We evaluated the involvement of nitric oxide (NO) in the early hemodynamic response to uninephrectomy (UNX) in rats. Animals were uninephrectomized, a nd 48 h after removal of the kidney, the effect of infusing N-G-nitro-L-arg inine methyl ester (L-NAME) on renal function was studied. Glomeruli were i solated, and glomerular nitrite and cGMP productions were measured. In addi tion, endothelial constitutive NO synthase (NOS III) and inducible NO synth ase (iNOS) were assessed by Western blot and by measuring the conversion of arginine to citrulline. UNX animals showed an increase in renal plasma flo w that was inhibited by L-NAME in a higher proportion than in sham-operated (SO) animals. No differences were observed in systemic NO-dependent vascul ar tone, since mean arterial pressure showed similar increments in SO and U NX rats. Glomeruli from UNX animals showed an increase in glomerular nitrit e production that was blunted by L-NAME addition. Also, cGMP levels were in creased in glomeruli from UNX animals, and this increase was inhibited by L -NAME. Western blot analysis showed no differences in NOS III but a higher iNOS amount in glomeruli from UNX than in those from SO rats. No significan t differences between UNX and SO rate were found in calcium-dependent NOS e nzymatic activity in the renal cortex. However, calcium-independent enzymat ic activity was markedly higher in the renal cortex of UNX than in those fr om SO animals. In conclusion, glomeruli from rats 48 h after UNX had a grea ter production of NO than those from SO animals. This increased glomerular NO production is based on an increase in the iNOS isoform. Increased glomer ular NO synthesis seems to play a role in the decreased renal vascular resi stance observed after unilateral nephrectomy in rats.