SummaryFour different heparin preparations - sodium and calcium salts of the same batch of heparin (mean molecular weight 15,000), low molecular weight sodium heparin (mean m. w. 9,000) and high molecular weight sodium heparin (mean m. w. 22,000) were injected subcutaneously on different days each into 6 healthy young volunteers in a randomized trial. Plasma heparin levels were measured using the anti-Xa assay at 1 hour, 3-4 hours and 6-7 hours after the injection. The highest anti-Xa potentiating effect was obtained after the injection of the low molecular weight sodium heparin (mean 0.381 i. u./ml) at 3-4 hours after the injection. With sodium heparin (m. w. 15,000) the highest values (0.135 i. u./ml) were found at 1 hour. Significantly lower anti-Xa potentiating effect was obtained 1 hour after the injection of calcium heparin and in particular after the injection of high molecular weight heparin (mean values 0. 072 i. u./ml and 0.043 i. u./ml respectively). Both these preparations showed an increase from 1 hour after injection to 3-4 hours after injection (mean values 0.082 i. u./ml and 0.057 1. u./ml at 3-4 hours after injection).These results indicate that the salt and the molecular weight of the preparation may strongly influence the degree of anticoagulation achieved after subcutaneous injection.

Christie, Graham-Stewart & Ingram (1960) described an abdomino-perineal excision of the rectum in a haemophilic of moderate severity who received animal antihaemophilic globulin (AHG) to cover the operation and post-operative period. Responses to this material were measured by assaying the AHG activity in the patient's plasma before and after each dose; and on two occasions the responses were strikingly high. These peaks corresponded to episodes of acute haemorrhage requiring immediate blood transfusion; and there was also an intermediate peak coinciding with a lesser haemorrhage insufficient to necessitate transfusion. It was not clear whether the high responses correlated with the severity of the bleeding or with blood transfusion; but in another haemophilic an unexpectedly high AHG level was associated with haematemesis while the patient was under observation only. It seemed therefore that haemorrhage was the correlated factor; and in considering a possible mechanism, the extensive previous work on the acceleration of blood coagulation after the administration of adrenaline was recalled: this was reviewed by Forwell (1955), and the problem was reexamined by Forwell & Ingram (1957), who thought at that time that the effect depended on an increase in the activity of Factor V. A possible explanation of the observations in the haemophilics was that haemorrhage had led to a release of adrenaline (Greever & Watts, 1959), and that this had in turn brought about an increase in the activity of AHG in the patients' plasmas. Forwell & Ingram (1957) had not examined AHG in their experimental subjects who had received adrenaline; it therefore seemed of interest to extend the earlier work to include AHG. The results of these experiments are now presented. METHODS The healthy experimental volunteers taking part in the present investigation were senior male medical students. The haemophilic subjects were adult patients, also of course, males, and in good health apart from their haemophilia. Neither they nor the healthy subjects were fasted before testing.

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SUMMARY1. Human subjects received intravenous infusions of adrenaline preceded by saline, phentolamine (an a-blocker) or either pronethalol or propranalol (fl-blockers), in different experiments.2. Clinical measurements of blood pressure and pulse rate confirmed that oc-or ,-blockade had been achieved.3. The rise in clotting factor VIII induced by adrenaline was blocked by pronethalol and propranalol but not by phentolamine. This indicated that the effect of adrenaline on factor VIII was mediated by f-receptors.

A solid phase non-competitive immunoradiometric assay (IRMA) has been developed which allows measurement of factor VIII related antigen (VIIIR:AG) levels in normal plasma as low as 2.5 x 10(-4) U/ml. The assay is based on the extraction of VIIIR:AG from test plasma by means of polystrene tubes coated with a specific unlabelled anti-VIIIR:AG rabbit antiserum and subsequent labelling of the extracted antigen with 125I-labelled anti-VIIIR:AG rabbit IgG.