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.