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The inhibitory effect of Separan AP-30, an anionic polyacrylamide, on atherosclerotic plaque formation in aortas of rabbits on a high (2%) cholesterol diet was tested over a period extending from 37 to 170 days. Atherogenesis was quantified morphometrically by application of a computerassisted image analysis of histologic cross sections of the aorta. The area of vessel wall-atheroma interface, fraction of lumen occluded, and other indexes of atherogenesis were measured in each of 26 segments of aorta excised from the animals, half of which were administered injections (intravenous) of Separan three times a week. Regression analysis of the morphometric data indicates that the polyelectrolyte exerts a powerful antiatherogenic effect in all regions of the aorta, inhibiting the formation of plaque mass to less than half in the aortic arch and about one-fifth in the descending aorta as compared with the aortic plaque masses in untreated rabbits. Results are compatible with the suggestion that a novel hemodynamic principle in vivo, polymer drag reduction, might be effectively applied against atherosclerosis. Circulation 75, No. 3, 627-635, 1987. THE ADDITION of certain linear macropolymers to flow can under certain conditions greatly reduce frictional resistance by polymer drag reduction, an effect also known among hydrodynamicists as the "Toms phenomenon." Flow can thus be increased by threefold or more without alteration of the driving pressure.'-3The effect occurs only in the presence of disturbed or turbulent flow, and it is associated with a laminarization of the flow. This phenomen has also been observed in pipe blood flow with at least four different drag-reducing polymers, 7 including the anionic polyacrylamide Separan AP-30.Application of the polymer drag-reduction principle to blood flow in vivo was first attempted independently From the

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SUMMARY1. The exchange of cellular Mg with external 28Mg in the rat left ventricle was measured in vivo and, under conditions approximating a steady state, in an isolated, working rat heart perfused and contracting at 36-38°C.2. About 98 % of cellular Mg exchanged at a single rate.3. The rate of exchange in vivo was the same as that observed in independent in vitro measurements of the influx and efflux at the physiological external Mg2+ concentration of 0-56 mm. The rate was 0-15 + 0-02 mmole/(kg dry ventricle. min) or 0-21 + 0-02 p-mole/(cm2.seC).4. In the perfused heart the dependence of the influx on the external Mg concentration was hyperbolic with an apparent Vmax of 0-31 + 0-04 mmoles/(kg dry weight. min) and an apparent K_ of 0-57 + 0-08 mM.5. The Mg efflux into a solution containing 2-8 mM-Mg was markedly faster than that into a Mg-free solution.6. These results are interpreted as consistent with a carrier-mediated transport of Mg across the plasma membrane.