Evaluation of kidney function in vasopressin-deficient rats by using dynumic enhanced MRI

Abstract

Objective To evaluate the renal function response to vasopressin in obstructed and non-obstructed kidney in vasopressin-deficient rats by using dynamic enhanced MRI. Methods This study included 26 vasopressin-deficient Brattleboro(BB)rats.Unilateral ureteral obstruction(UUO) model was set up in 12 BB rats.After releasing UU0 24 h,treatment of AVP was given in 7 non-obstrueted and 7 obstructed BB rats for 6 d.Seyen normal Wistar rats and 7 BB rats were used as control.Dynamic enhanced MRl was performed at 0-60 min following the administration of GadoliniumDTPA(0.05 mmol/kg)and the mean relative signal intensity(RSI)was measured. Results BB rats RSI increase occurred during the first minute,with a maximum mean RSI of(149±10)%in cortex,(155±13)%in medulla and(146±13)%in pelvis.Then,a gradual decrease in the cortical RSI occurred,after which a small increase was observed in Phase 3.BB rats RSI patterns were different from Wistar rats.After AVP treatment,mean RSI of BB rats in cortex,medulla and pelvis reached a maximum of(180±6)%,respectively at 30 sec,followed by a fast decrease at 1 min.Then,RSI decreased gradually.Phase 3 demonstrated a moderate increase in medullary and a relative large increase in pelvic RSI until 30 min after injection,after which RSI returned to baseline.BB rats RSI patterns after AVP treatment were similar to that of Wistar rats.Cortical,medullary and pelvic mean RSI increased slowly compared to non UUO rats.In phase 3,mean RSI of all segments decreased gradually.UUO rats RSI patterns were different from non UUO rats.After AVP treatment in UUO rats,mean RSIs of all segments increased faster compared to UUO rats without AVP.Cortical mean RSI reached a maximum of(193±7)% at 2 mim Mean RSI of medulla were unchanged,but the pelvic mean RSI deereased gradually to a minimum of(77±5)%at 5 min.Phase 3 was characterized by a slight recovcry of all RSIs.UUO rats RSIs were recovered after AVP treatment.The renal blood flow(RBF)of UUO rats was decreased to(1.1±0.1)m1·min-1·100g-1,wherease the RBF was increased to (1.9±O.3)ml·min-1·100g-1 after injecting AVP. Conclusion Dynamic enhanced MRI may provide useful information for distinguishing between kidneys having changes in the renal vasopressin concentration and the kidneys suffer from the obstructed renal damage. Key words: Magnetic resonance image; Kidney function; Rrats brattleboro; Vasopressins