ASSESSMENT OF CHANGES IN INTRARENAL BLOOD-FLOW IN CONSCIOUS RATS USING LASER-DOPPLER FLOWMETRY

The present study was designed to develop, for the first time, a metho d that allows long-term repeated measurements of renal cortical blood flow (CBF) and medullary blood flow (MBF) in conscious unanesthetized rats. The use of fiber-optic probes (0.5 mm diam) for the chronic meas urement of renal CBF and MBF was evaluated. Basal renal cortical and m edullary laser-Doppler flow (LDF) signals and the responses to intrave nous bolus injections of angiotensin II (ANG II, 12.5 ng) were determi ned every other day for 11 days in conscious Sprague-Dawley rats (n = 9). A recovery period of 5-7 days after surgery was required before st able signals were obtained from the implanted probes. Thereafter, the fiber-optic probes gave reproducible laser-Doppler measurements of CBF and MBF for 11 days. The CBF and MBF responses to intravenous bolus i njections of ANG II (12.5 ng) were also constant during this period. C hronic implantation of the fiber-optic probes caused minimal tissue da mage and did not significantly alter urine concentrating ability or re nal function. These findings suggest that LDF technique with chronical ly implanted optical fibers provides a new tool for the continuous lon g-term monitoring of regional blood flow in the kidney of conscious ra ts.