Estimation of rat muscle blood flow by microdialysis probes perfused with ethanol, [C-14]ethanol, and (H2O)-H-3

We used the perfused rat hindquarter to evaluate whether the microdialysis ethanol technique can be used to qualitatively estimate nutritive skeletal muscle blood flow. Four microdialysis probes were inserted in different hin dlimb muscles in each of 16 rats. Hindquarters were perfused at blood flow rates ranging from 0 to 21 ml 100 g(-1) min(-1). The microdialysis probes w ere perfused at 2 mu l/min with perfusate containing ethanol, [C-14]ethanol , and (H2O)-H-3. Within and between experiments outflow-to-inflow ratios (o /i) generally varied inversely with blood flow. When a low flow or no flow was maintained in hindquarters, o/i ratios first increased with time (for a t least 60 min) and then leveled off. The long time constant impaired detec tion of rapid oscillations in blood flow, especially at low blood flow rate s. Contractions per se apparently decreased o/i ratios independent of blood flow. Ethanol and [C-14]ethanol o/i ratios did not differ. (H2O)-H-3 o/i p aralleled ethanol and [C-14]ethanol o/i ratios but it was significantly low er. In conclusion, differences in skeletal muscle blood flow can be detecte d by the microdialysis technique. However, the slow changes in o/i, in part icular at low blood flow rates, limit the usefulness of the technique for m easuring dynamic changes in blood flow; caution must also be exerted during muscle contractions. (H2O)-H-3 and [C-14]ethanol are good alternatives to ethanol in the determination of blood flow by microdialysis.