Measurement of renal artery pressure in the rat.

The objective of this study was to develop and document a simple technique for the direct measurement of renal artery pressure (RAP) in the rat. RAP was recorded in 13 Sprague-Dawley rats using a glass micropipette fitted to a low displacement pressure transducer. Average mean arterial pressure recorded from a femoral artery catheter was 107.2 +/- 3.2 mmHg compared with a RAP of 103.8 +/- 3.7 mmHg (P less than 0.05). To determine whether the measurement affected renal blood flow (RBF), RBF was determined using radiolabeled microspheres, both before and while recording left RAP. No differences existed between the initial left and right RBFs [7.3 +/- 0.4 %CO/gm (percent cardiac output per gram tissue) vs. 7.3 +/- 0.4 %CO/gm, P greater than 0.9]. The micropipette in the left renal artery did not alter left RBF (control, 7.3 +/- 0.4 %CO/gm vs. experimental, 7.6 +/- 0.4 %CO/gm; P greater than 0.2). Right RBF did not change between successive flow determinations (P greater than 0.5) indicating that a change in renal hemodynamics unrelated to the protocol did not occur. The techniques presented provide an accurate, simple method for the direct measurement of RAP in the rat.