Hazelett SE, Preusch PC. Tissue distribution and warfarin sensitivity of vitamin K epoxide reductase.
Biochem Pharmacol 1988;
37:929-34. [PMID:
3345202 DOI:
10.1016/0006-2952(88)90183-9]
[Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The distribution of vitamin K epoxide reductase activity and its sensitivity to warfarin have been examined in whole microsomes from tissues of both control and warfarin-resistant strain rats. The distribution of activity roughly paralleled that previously shown for the vitamin K-dependent carboxylase. Activity on a per gram tissue basis was highest in kidney, adrenal, spleen, lung, testes, and epididymis at a level about 1/20th of that present in liver microsomes. Vitamin K quinone formation by microsomes from warfarin-resistant rats was approximately half that of control strain samples. In addition, hydroxy vitamin K was formed by warfarin-resistant strain microsomes to about the same extent as vitamin K quinone in all tissues. The Km values for dithiothreitol (DTT) and vitamin K epoxide were similar in all tissues (range = 0.1-0.2 mM DTT at 40 microM vitamin K epoxide, and 10-30 microM vitamin K epoxide at 2 mM DTT). The sensitivities to warfarin were similar for all control strain rat tissues (I50 = 10-20 microM at 2 mM DTT and 40 microM vitamin K epoxide) and similarly elevated for all warfarin-resistant rat tissues (I50 = 30 to greater than 80 microM). These results suggest that the identical enzyme is expressed in all tissues and that tissue specific isozymes do not occur.
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