Preparation of the inguinal fat pad for perfusion in situ in the rat: a surgical technique that preserves continuous blood flow.

We developed a surgical technique for preparing the inguinal fat pad of rats for perfusion that preserves continuous blood flow to the tissue. Fatty acid uptake from the fat pads of fed rats (46.1 +/- 2.1% of arterial supply, n = 82) and release from those of fasted (48 h) animals (51.3 +/- 3.1% of supply, n = 69) occurred principally via the free fatty acid component of the blood; levels of triglycerides, cholestryl esters, and phospholipids did not change significantly. Venous blood flow in perfusions using blood from fed rats was 83.3 +/- 1.7 mL/min and 83.1 +/- 1.5 microL/min in experiments involving fasted donors. Values for arterial (A) and venous (V) pH (A, 7.41 +/- 0.03; V, 7.32 +/- 0.04), pO2 (A, 151.6 +/- 15.7 mm Hg; V, 34.7 +/- 9.2 mm Hg), pCO2 (A, 30.8 +/- 6.6 mm Hg; V, 58.2 +/- 5.2 mm Hg), and hematocrit (A, 44.6 +/- 1.2%; V, 45.7 +/- 1.2%) were unchanged throughout the course of the perfusions. Fat pad and blood perfusates were maintained at 37 degrees C. Tissue homogenates revealed that the total fatty acid content of fat pads from fed rats (333.5 +/- 0.3 mg/g tissue) differed significantly from that in fasted animals (260.7 +/- 0.7 mg/g tissue; P < 0.001). Our technique likely will have many uses in the study of lipid transport and metabolism, hyperlipidemia, and cancer-associated cachexia.