METHODS

Experimental conditions. Fourteen male subjects were studied. Nine were medical students and laboratory col-leagues and five were ambulatory convalescent patients. No food was permitted after 6: 00 PM the previous night. Blood samples were collected between 10: 00 AM and 1: 00 PM, that is, 16 to 19 hours postprandially. Subjects lay supine in an air-conditioned room maintained at 25 C. with the arm comfortably supported. The procedure was previously explained to the subjects and there was little overt anxiety. The brachial artery was cannu-lated with an 18-gauge thin-walled Riley needle so that the tip of the needle lay just proximal to the antecubital crease. Venous blood for measurement of metabolite concentrations was collected through a polyethylene catheter (I. D. 0.86 mm., 0. D. 1.27 mm.) passed through a 16-gauge thin-walled needle which had been introduced in a retrograde direction through a large antecubital vein and into one ofthe deep veins draining the forearm muscles. Another catheter was similarly passed into any superficial forearm vein for the collection of blood used only in validating the blood flow method. Blood flow through wrist and hand was excluded during the experimental periods by a 10-cm. wide pressure cuff about the wrist inflated to a pressure at least at 100 mm. Hg greater than systolic. Blood flow was measured by the dye-dilution method previously described (8). In brief, a 0.25 per cent aqueous solution of Evans blue dye, T-1824, in0. 9 per cent sodium chloride was introduced continuously at a constant rate into the brachial artery. The dye concentration was measured in two venous blood samples obtained simultaneously. Flow was calculated from the mean dye con-centration only if there was good agreement in the two samples (8).