Evidence for the Release of Individual Amino-acids from the Resting Human Forearm

Journal/Book: Reprinted from Nature Vol. 208 No. 5010 pp. 588-589 November 6 1965. 1965;

Abstract: D. R. LONDON T. H. FOLEY Departments of Chemical Pathology and Medicine St. Thomas's Hospital Medical School London S.E.I. C. G. WEBB Institute of Computer Science University of London London W.C.1. THE study of differences in concentration of substances in arterial and venous blood is well-documented and offers a method for investigating peripheral metabolism. In order to study this aspect of amino-acid metabolism in man cannulation of the brachial artery and brachial vein of the same limb1 was carried out in six subjects four of whom were normal one convalescing from a myocardial infarction and one suffering from benign essential hypertonsion. All the experiments were carried out at 10 a.m. after an overnight fast. Two simultaneous arterial and venous blood samples were withdrawn from each individual; there was an interval of 30 min between the pairs of specimens. Immediately before and again after a blood sample had been taken the forearm blood-flow was measured by plethysmography with a mercury-inrubber strain-gauge2 and was shown to be constant. During the blood-flow measurements and while the samples warn being taken an occluding cuff around the wrist was inflated to a pressure that was 100 mm mercury above the systolic blood pressure. Soon after the blond had been withdrawn it was centrifuged in the cold the plasma protein precipitated with 1 per cent picric acid3 and stored at -15° C until analysed by automatic ion-exchange chromatography4. The means of the two arterial and the means of the two venous amino-acid measurements from each person were used for calculating the mean differences found in the group. Table 1 shows the mean difference in venous and arterial amino-acid concentrations expressed as a percentage of the arterial concentration and also the differences themselves in µmoles/100 ml. plasma. in the group of six subjects. The significance of the differences calculated by testing against the null hypothesis using both tails of the ´t' distribution5 is also shown. During the time taken for the experiment there was no evidence of a downward drift in either arterial or venous concentrations. ... ___MH

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