To estimate the glomerular filtration rate (GFR) in conscious rabbits, a 
single-sample method using the non-ionic contrast medium iodixanol was compared 
with a three-sample method using the standard agent inulin. Iodixanol and inulin 
were co-administered intravenously to male New Zealand White rabbits at 60 mg 
I/kg and 40 mg/kg, respectively, and blood was collected 30, 60, 90 and 120 min 
later. Serum iodixanol and inulin concentrations were separately determined by 
high performance liquid chromatography and colorimetry, respectively. Serum urea 
nitrogen (UN) and creatinine concentrations were also determined. Based on the 
data from healthy and cisplatin-treated rabbits, the GFR estimated by iodixanol 
was well consistent with that by inulin. Further, when the GFR decreased to more 
than 60% of the reference value, serum creatinine concentrations became 
elevated. However, serum UN concentrations exhibited wide fluctuations, 
presumably due to a difference in renal handlings. The single-sample method 
using iodixanol was considered to be an expedient tool in both clinical and 
research settings, because the stress due to a multi-sample method was reduced.