Sufficient radiation will cause kidney injury with hypertension, azote
mia, and death from renal failure. There is early endothelial injury a
fter radiation, which could lead to a deficit of constitutive nitric o
xide (NO) synthesis, with capillary thrombosis and hypertension, both
of which are seen in radiation nephropathy. In a rat radiation nephrop
athy model, the serial evolution of urinary cyclic guanosine monophosp
hate (cGMP), a marker of kidney NO, was studied and a deficit in urina
ry cGMP was found. This radiation-induced cGMP deficit was prevented b
y high-dose Captopril treatment Low-dose Captopril treatment protected
against radiation nephropathy without preventing the decrease in urin
ary cGMP. An inhibitor of NO synthesis, L-N-arginine-methylester, did
not blunt the beneficial effect of Captopril treatment. We conclude th
at there is a deficit in urinary cGMP in radiation nephropathy, but th
at prevention of this deficit is not essential in the prevention of ra
diation nephropathy by Captopril.