Using BOLD Imaging to Measure Renal Oxygenation Dynamics in Rats Injected with Diuretics

PURPOSE: we used blood oxygenation level-dependent magnetic resonance imaging (BOLD MRI) to measure renal oxygenation dynamics in rats injected with diuretics and evaluated diuretic effect on renal oxygenation. METHODS: we performed BOLD MRI studies in 32 rats using a 1.5-tesla MR imaging system for animal experiments. We intravenously injected rats with saline (n=7), furosemide (n=7), acetazolamide (n=6), or mannitol (n=6). For controls, 6 rats were not injected with drugs. We estimated the apparent transverse relaxation rate (R(2)*) from the apparent transverse relaxation time (T(2)*)-weighted images and measured the time course of R(2)* at 4-min intervals over approximately 30 min. RESULTS: compared with preadministration values, the R(2)* value did not change significantly in either the cortex or medulla in the control and mannitol groups but decreased significantly in the saline group; the R(2)* value significantly decreased in the medulla but did not change significantly in the cortex in the furosemide group; and the R(2)* value significantly increased in the medulla and significantly decreased in the cortex in the acetazolamide group. CONCLUSION: our study results suggest that BOLD MRI is useful for evaluating the dynamics of renal oxygenation in response to various diuretics in the renal cortex and in the medulla.