INTRODUCTION: FM are gaining wide acceptance for use in measuring regional BF. This study was designed to evaluate inter-animal variation in baseline BF and intra-animal variation based on paired organ BF comparisons in normal rats. METHODS: Male S-D rats (350-450g, n=33) were anesthetized with ketamine and catheters (PE-50) were advanced into the left ventricle (LV) and abdominal aorta caudal to the renal arteries. Blue-green FM (0.2x10⁶ spheres in 0.2 ml) were injected into the LV over 3s followed by a 0.2 ml saline flush. Reference blood was withdrawn at a rate of 0.5 ml/min 5s prior to FM injection and 30s following the flush. Tissues were digested in 4% KOH, FM extracted using vacuum filtration and dye extracted using Carbitol acetate. RESULTS: BF - ml/min/100g ww, mean±SE.

Heart	301±24	L Adrenal	401±58	Liver	23±2
L Lung	58±12	R Adrenal	534±62	Diaphragm	49±4
R Lung	71±13	Duodenum	310±18	Soleus m	10±1
L Kidney	554±28	Jejunum	219±24	Cortex	92±7
R Kidney	556±27	Ileum	121±10	Hindbrain	67±4
Spleen	130±7	Colon 63±6

CONCLUSIONS: FM can give reliable organ BF values during normal hemodynamic function in rats. The similarity between paired organs confirms the uniformity of FM suspensions as well as adequate mixing in the LV. Reliability of this technique during low-flow states in rats remains to be determined.

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