Antithrombin III deficiency: decreased synthesis of a biochemically normal molecule.

A 29-yr-old white female has suffered from recurrent venous thromboses over the last 12 yr. Plasma antithrombin III (AT-III) levels were 48% of normal by immunoelectrophoresis and 56% by chromogenic assay. Three of four siblings and the father had similar AT-III levels without associated venous thromboses. Heparin-Sepharose chromatography demonstrated normal behavior of the patient's AT-III. Her purified AT-III could not be distinguished from AT-III purified from a normal control either by SDS polyacrylamide gel electrophoresis or by crossed immunoelectrophoresis, and the heparin cofactor activity and the progressive antithrombin activity of both AT-III samples were identical. Turnover studies were made in the patient using her own purified AT-III labeled with 131I, (*I). The results did not differ significantly from studies made with autologous *I-AT-III in two normal control women. Her fractional breakdown rate of 0.54 total plasma AT-III per day compared with 0.45 and 0.52 in the controls. These studies indicate that the patient synthesizes a normal AT-III molecule at half normal rates.

Biochemical and functional study of antithrombin III in newborn infants.

Antithrombin III (AT-III) was isolated by heparin affinity chromatography from adult venous and newborn term and preterm umbilical cord blood. The purified proteins were compared by SDS-PAGE, rocket immuno-electrophoresis, protein concentration by microbiuret relative to optical density at 280 nm, heparin cofactor specific activity, progressive neutralization of thrombin and factor Xa at 37 degree C and pH related antithrombin kinetics. The structural evaluations revealed a fetal AT-III of molecular weight, charge and electrophoretic migration indistinguishable from adult AT-III. The functional studies showed that, on an equimolar basis, the rates of thrombin and Xa interactions with fetal AT-III were as rapid as those with adult AT-III. The catalytic rates of various concentrations of heparin were also equal. The newborn infant, therefore, displays a quantitative but not quantitative deficiency of AT-III.

Effects of prostaglandin E2, analogs, fatty acids, and indomethacin on fibrinogen level.

Dose-response relations in rabbits for 3-h intravenous infusion of prostaglandin E2 (PGE2) and (15S)-15-methyl-1-prostaglandin E2 methyl ester (MePGE2) on plasma fibrinogen and systolic blood pressure were determined and described by regression equations. MePGE2 was 20 times more active than PGE2. Fibrinogen synthetic rate responses to PGE2 and MePGE2 were estimated. Infusion of the PGE2 precursor, arachidonic acid, elevated plasma fibrinogen, but fibrinogen response to 0.5-9 mg/kg arachidonic acid was unrelated to dose and half that given by 3 mg/kg PGE2. Slow infusion of several other fatty acids raised plasma fibrinogen as effectively as arachidonic acid, but prostaglandins D2 and F2alpha had only a slight effect. Infusion of 30 times the indomethacin dose that blocks platelet prostaglandin synthetase did not alter the plasma fibrinogen response to arachidonic acid. Indomethacin did not inhibit plasma fibrinogen elevations following ACTH or endotoxin infusion, or subcutaneous turpentine injection. Intravenous infusion of two cyclic ether prostaglandin endoperoxide analogs, (15S)-hydroxy-9alpha, 11alpha-(epoxymethano) prosta-5Z, 13E-dienoic acid, and (15S)-hydroxy-11alpha, 9alpha(epoxymethano) prosta-5Z, 13E-dienoic acid, failed to increase plasma fibrinogen.

Fibrinogen synthesis stimulation by prostaglandin E1 and some other vasodilators.

Three-hour constant-rate intravenous infusion into rabbits of 1-3 mg prostaglandin E1 (PGE1) per kilogram markedly increased plasma fibrinogen 24 h later. 131I-labeled fibrinogen and model studies showed increased synthesis underlay this. Similar PGE1 doses lowered systolic blood pressure. Maintaining systolic blood pressure by infusing noradrenaline with the PGE1 did not alter plasma fibrinogen response to PGE1; plasma fibrinogen was unchanged by noradrenaline infusion. Regression equations relating plasma fibrinogen increment to PGE1 dose, plasma fibrinogen increment to dose and systolic blood pressure change, and systolic blood pressure change to dose are given as well as the constants relating plasma fibrinogen increment to dose using the Michaelis-Menten equation. Infusions of cyclic AMP, dibutyryl cyclic AMP, and cyclic GMP intravenously led to only small plasma fibrinogen increases. Daily intravenous infusions of PGE1 led to loss of both plasma fibrinogen and systolic blood pressure responses in two animals; a third animal showed only loss of the former and a fourth only loss of the latter response. PGE1 slightly enhanced the small plasma fibrinogen increase following intravenous bradykinin. Approximate arterial blood PGE1 concentrations resulting from the intravenous infusion of 1 mg mg PGE1 kg-1 3 h-1 are calculated. These are compared with measured values.