| 释义 |
prothrombin Phys.|prəʊˈθrɒmbɪn|
[a. G. prothrombin (A. Schmidt Zur Blutlehre (1892) xii. 202), f. Gr. πρό pro-2 + θρόµβ-ος clot, thrombus: see -in1.]
A protein formed in the liver and normally present in blood, whose conversion into thrombin is an essential part of the clotting process.
1898E. A. Schäfer Text-bk. Physiol. I. 160 A fibrin ferment (thrombin), or its precursor (prothrombin), producing the formation of fibrin from fibrinogen. Ibid., The fibrin ferment is sometimes spoken of as ‘thrombin’, and the nucleo-proteid material in the plasma from which it is produced is then termed ‘prothrombin’. 1912J. G. McKendrick Princ. Physiol. viii. 117 The theory at present in vogue is that when blood is shed there is at once the death of many colourless cells. These contain a protein called pro-thrombin, which, in turn, produces an enzyme known as thrombin. 1936[see hypoprothrombinæmia s.v. hypo- II]. 1946[see oxalated ppl. a. s.v. oxalate v.]. 1957Sci. News XLIV. 31 In the presence of ionized calcium, of a further globulin component of the plasma, and probably of other factors, thromboplastin converts prothrombin, by what must be a relatively minor change in its molecule, to thrombin. This last substance now reacts directly with fibrinogen, changing it to fibrin. 1974R. M. Kirk et al. Surgery ii. 10 Vitamin K analogue, 10 mg intramuscularly each day, replaces the deficiency but if there is concomitant liver damage, prothrombin is not synthesised. 1976[see proconvertin s.v. pro-2 1].
b. attrib., as prothrombin time, the time taken for blood or plasma to clot when an excess of a calcium salt and possibly other natural components of the clotting mechanism (besides prothrombin) are added.
1935Amer. Jrnl. Med. Sci. CXC. 505 By omitting the addition of excess thromboplastin, but otherwise following the directions of the method outlined for the determination of prothrombin, one determines the clotting time of recalcified plasma, which for normal plasma is from 90 to 130 seconds. This method is still commonly called Howell's Prothrombin Time. 1957A. J. Quick Hemorrhagic Dis. ii. 44 The prothrombin time of normal human plasma is consistently 12 seconds, whereas when measured by the two-stage test, it varies from 244 to 452 units. 1972Daily Colonist (Victoria, B.C.) 1 Feb. 2/1, I am on anticoagulants and have a prothrombin time test taken weekly to determine dosage. |