The Determination of Platelet Aggregation by Filtration Pressure in Circulating Dog Blood

Abstract

SummaryA reproducible method is described for quantitating either spontaneous or ADP- induced platelet aggregation in circulating dog blood after heparinization. An extra- corporeal shunt containing screen material with openings 53 microns square was placed in the dog’s arterial circulation. The blood pressure was measured proximal to this filter. The blood pressure decreased upon opening the shunt to the circulation and increased when the filter became occluded. The degree and rate of aggregation was determined by means of measuring these blood pressure changes. Phase and electron microscopy demonstrated platelet aggregates occluding the filters. Platelet aggregation on the filter was experimentally accelerated by infusing ADP before the filter. The administration of ADP in concentrations between 0.625 and 10 μg/ml until occlusion, produced a dose response relationship between log of ADP concentration and rate of filter occlusion. Macrodex, a known inhibitor of platelet aggregation was given intravenously and was found to delay filter occlusion. Similar results were obtained with high intravenous doses of phenylbutazone. The method was used to compare the drug effects with their in vitro effects measured photometrically. It would appear that this technique can be used for demonstrating and quantitating the effects of drugs on the process of platelet adhesion and aggregation in vivo.

Effect of 1-Methyl-2-Mercapto-5-(3-Pyridyl)-Imidazole (KC-6141), an Anti-Aggregating Compound, on Experimental Thrombosis in Rats

“…The poor blood flow through the shunt due to bad operation and due to blood coagulates on the tubing wall diminished significantly the formation of thrombus (Umetsu and Sanai, unpublished data). So the formation of thrombus is affected by both the concentration of platelets in circulating blood and the blood flow rate, as shown in the filter loop technique of Broersma et al (1973).…”

“…This is also supported by the fact that the development of thrombus occurred after heparinization in this study and by the evidence that inhibition of blood coagulation by the continuous injection of heparin did not affect the development of platelet thrombus . In this respect, this method appears to be similar to the filter loop technique which measures platelet aggregation in flowing blood in vivo (Broersma et al 1973, Muirhead 1973.…”

In Vivo Antiaggregatory Action of Platelet-Activating Factor in Beagle Dogs: Role for Prostacyclin

“…Briefly, an arteriovenous bypass was formed between the right femoral artery and vein. The arterial blood was directed through an extracorporeal filter with 30 pm pores by a roller pump at a constant rate of 15 ml min-l. A few minutes after pumping the blood through the filter the perfusion pressure, measured proximal to the filter by an electromanometer (EM 3L, Medicor, Budapest, Hungary) using a Statham P50 strain gauge (Hato Ruy, PR), started to increase linearly as a result of spontaneous platelet aggregation (8,9,10). Platelet aggregation was quantitated by calculating filter occlusion rate and filter occlusion time (8).…”