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A survey of the distribution of prostaglandins E1, E2, F1α and F2α in fourteen tissues from the dog, cat, rat, rabbit, guinea‐pig and chicken has been made. One or more of these prostaglandins are present in varying amounts in most tissues with PGE2 PGF2α occurring most commonly.

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A method has been developed for the immunological quantitation of factor VIII:C Ag using a medium titre (50 new Oxford units) factor VIII:C antibody arising in a severe multitransfused haemophiliac. The method, which utilizes clotting inhibition in an agarose gel medium, gave close and significant correlation with the two-stage factor VIII:C procoagulant assay (r=0.83, P less than 0.01) for 54 normal subjects. Similar or higher values were found in 19 mild, moderate and severe haemophiliacs with 2-30% average normal plasma levels of factor VIII:C (r=0.72, P less than 0.01). Four mild von Willebrand patients gave similar results by immunoassay and procoagulant assay methods. A previously identified patient with cross reacting material (CRM+) gave an immunoassay within the normal range (66%) with only 4% VIII:C activity detectable. The method offers a simple, sensitive and apparently reliable procedure for the assay of plasma factor VIII:C Ag which may prove useful in the further investigation of factor VIII:C Ag and antibody heterogeneity. The procedure offers an alternative to immunoradiometric assay and may be of potential use in the assessment of the haemophilia carrier state and possibly the early detection of thrombosis.

SUMMARY Plasma antithrombin levels were measured by clotting, immunological, and amidolytic methods on two groups of subjects: 20 normal individuals and nine patients studied serially postoperatively (hip replacement). The postoperative patients were observed for the emergence of deep-vein thrombosis using 1251-fibrinogen uptake measurements (FUT).The three methods gave similar ranges for the normal subjects, were reproducible (cv < 5 %), and detected early postoperative reduction of antithrombin levels. All three methods failed to show any significant differences in preoperative antithrombin levels between the positive and negative FUT groups.Correlation studies were performed on the pooled data from the normal and postoperative group (range 60-130% of normal; 100 samples). The best correlation (r = 0 75; P < 0 01) was achieved with the chromogenic kit assay method versus the Mancini immunoassay technique. The thrombin agarose (total antithrombin) gel diffusion technique correlated less well with the chromogenic (r = 0-65; P < 0.01) and Mancini immunoassay (r = 0 45; P < 0 01) methods. It is concluded that the chromogenic kit method gives a rapid, reproducible, and specific measurement of antithrombin III. The thrombin agarose diffusion method, though not specific for antithrombin III, is a cheap and simple method to perform. The potential of the three methods for detecting the prethrombotic stage and early thrombosis is discussed.Current interest in the relationship between thrombosis and antithrombin levels is complexed by the variety of methods available for the measurement of this natural anticoagulant' and the variable reliability of methods for the detection of thrombosis.