Summary. Controlled perfusion through the lumen of the distal cauda epididymidis in the anaesthetized rat has been explored as a means of examining physiological exchanges from blood across the epididymal epithelium. The mean length of the perfused, sperm-free, tubule was 14·5 cm (±1·5 s.e.m., n = 9). No cholesterol, protein or sialic acid was detected in the perfusate at flow rates exceeding 10 μl/min, but at rates of 0·4–1·2 μl/min, protein appeared at concentrations of 0·21–0·55 mg/ml (i.e. secretion rates of 0·21–0·83 μg/min; 3 rats). Glucose was detected at all perfusion rates (3–27 μl/min) at concentrations of 0·06–0·58 mm (0·8–6·8% blood levels).
During intravenous infusions of 3H2O, radioactivity in the perfusate rapidly attained 87% blood plasma concentrations; no radioactivity was detected when carboxy-[14C]dextran or methoxy-[3H]inulin were infused. Radioactivity appeared in the epididymal perfusate to 1–7% of blood levels during intravenous infusions of d-[U-14C]glucose or 3-O-methyl[1-3H]glucose.
This evidence suggests that the preparation is physiological and could be used to explore the dynamics of exchanges between blood and epididymis.