Vitamin K requirement and warfarin tolerance in the hamster.

A dietary deficiency of vitamin K has been demonstrated in the Syrian hamster. This species has also been shown to be relatively resistant to the action of the indirect anticoagulant Warfarin, and very sensitive to the anticoagulant action of the vitamin K antagonist chloro-K. These observations, and the hamster's apparently high requirement for the vitamin, indicate that it responds to vitamin K and vitamin K antagonists in the same fashion as Warfarin-resistant strains of rats.     

Comparative study of the effect of phenazine methosulfate and vitamin K3 on human erythrocytes by hemolysis curves]

Hemolysis curves were used for comparative study of phenazine methylsulfate (PMS) and vitamin K3 action on human erythrocytes. Some differences in PMS and vitamin K3 action were revealed while the concentration of studied compounds and incubation time with them were changed. It is considered that the observed differences in PMS and vitamin K3 action are caused by different degree of oxidation of intracellular hemoglobin.     

Anti-oxidant/pro-oxidant reactions of vitamin K

Experiments were designed to measure O2 consumption caused by the oxidation of linoleic acid. These experiments show that vitamin K has antioxidant activity and that the reduction in linoleic acid oxidation is directly dependent upon vitamin K concentration. Conversely, vitamin K hydroquinone enhances linoleic acid oxidation in the absence of iron catalyst, again in a concentration dependent manner. At equilmolar concentrations vitamin K is about 80% as effective as vitamin E as an antioxidant. Vitamin E inhibits the oxidation of linoleic acid catalyzed by vitamin K hydroquinone. Vitamin E also strongly inhibits vitamin K dependent formation of both vitamin K epoxide and gamma-carboxyglutamic acid (gla). The significance of these observations to vitamin K action in vivo is discussed.     

Metabolism of vitamin K and prothrombin synthesis: anticoagulants and the vitamin K--epoxide cycle.

Vitamin K is primarily located in hepatic microsomes, where the vitamin K-dependent carboxylation in prothrombin synthesis occurs. Recent evidence supports the idea that the carboxylation is linked to the metabolism of the vitamin--specifically the cyclic interconversion of vitamin K and vitamin K epoxide. The primary site of action of coumarin and indandione anticoagulants appears to be an inhibition of the epoxide-to-vitamin K conversion in this cycle. There is a correlation between the inhibition of prothrombin synthesis and the regeneration of vitamin K from the epoxide by anticoagulants. In hamsters and warfarin-resistant rats prothrombin synthesis and the epoxide-K conversion are less sensitive to warfarin than in the normal rat. The epoxide-K conversion is impaired in resistant rats, which may explain their high vitamin K requirement. There is also a correlation between vitamin K epoxidation and vitamin K-dependent carboxylation, but the apparent link may be because vitamin K hydroquinone is an intermediate in the formation of the epoxide and also the active form in carboxylation. The vitamin K-epoxide cycle is found in extrahepatic tissues such as kidney, spleen, and lung and is inhibited by warfarin.     

Role of Ca ions and protein kinase C in the action of vitamin E on respiratory burst of neutrophils and blast transformation of lymphocytes]

It was shown that vitamin E decreased the stimulating role of oxidative burst activators which influenced on Ca(2+)-dependent mechanisms (A23187, verapamil, FMLP). Jointly addition of this vitamin and blood plasma contained tocopherol-binding proteins influenced on mechanisms associated with protein kinase C. It was shown that Ca ions can also take part in tocopherol's action on blast transformation of lymphocytes.     

Activity of various enzymes of energy metabolism in the rat kidney and intestines in vitamin D and K deficiency

The vitamin D and K deficiency was studied for its effect on creatine kinase, phosphorylase and alkaline phosphatase activity of rat kidneys and intestinal mucosa. The results show that creatine kinase and phosphorylase activity of kidneys varies depending on the content of these vitamins, e.g. it is activated with vitamin D depletion irrespective of the vitamin K status and remains unchanged with the deficiency of vitamin K alone. In this case the vitamin D deficiency affects kidney phosphorylase and intestinal mucosa differently. Data obtained and those available in literature permit suggesting that the deficiency of the same vitamin may exert a different action on the activity of isoforms of such enzymes as creatine kinase and phosphorylase.     

Mechanism of coumarin action: sensitivity of vitamin K metabolizing enzymes of normal and warfarin-resistant rat liver

The in vitro effects of two coumarin anticoagulants, warfarin and difenacoum, on rat liver microsomal vitamin K dependent carboxylase, vitamin K epoxidase, vitamin K epoxide reductase, and cytosolic vitamin K reductase (DT-diaphorase) from the livers of normal and a warfarin-resistant strain of rats have been determined. Millimolar concentrations of both coumarins are required to inhibit the carboxylase and epoxidase activities in both strains of rats. Sensitivity of DT-diaphorase to coumarin inhibition differs when a soluble or liposomal-associated substrate is used, but the diaphorases isolated from both strains of rats have comparable sensitivity. The anticoagulant difenacoum is an effective rodenticide in the warfarin-resistant strain of rats, and the only enzyme studied from warfarin-resistant rat liver that demonstrated a significant differential inhibition by the two coumarins used was the vitamin K epoxide reductase. This enzyme also showed the greatest sensitivity to coumarin inhibition among the enzymes studied. These results support the hypothesis that the physiologically important site of action of coumarin anticoagulants is the vitamin K epoxide reductase.     

Vitamin d

The primary source of vitamin D is the skin, following exposure to ultraviolet radiation. Vitamin D is well known for its effects on stimulating calcium absorption and is thus essential for maintenance of normal bone. It is also important for muscle function and has more recently been implicated in protection against several diseases including diabetes. Different pathways of action have been described for vitamin D compounds and various analogs specific to these pathways have demonstrated potential for therapeutic use. Recent studies suggest a novel role for vitamin D compounds in protection against cancer, a proposal supported by substantial epidemiological evidence.     

Ineffectiveness of phylloquinone epoxide as an inhibitor of prothrombin synthesis in the rat

Phylloquinone epoxide (vitamin K₁-oxide), a metabolite of phylloquinone, does not inhibit prothrombin synthesis when administered in high doses to Sprague-Dawley and warfarin-resistant rats. Further, it does not accumulate to presumed inhibitory levels in the livers of rats given physiological doses of ³H-phylloquinone when they are anticoagulated with warfarin. These data do not support the Bell-Matschiner hypothesis that warfarin exerts its action by inhibiting the vitamin K oxide reductase which results in the accumulation of vitamin K oxide and the inhibition of vitamin K at its active site. Rather, our data support the view that vitamin K and warfarin combine at different sites with a single regulatory protein which serves as a conformational switch for prothrombin synthesis.     

维生素K2对肝脏的保护作用

急慢性肝损伤、肝硬化和肝癌等肝脏疾病是严重影响人类健康的重大疾病。肝脏是人体内最大的消化腺,是体内新陈代谢的中心站,也是肠道内容物及细菌代谢产物进入体内循环的必经之路。虽然由肠道吸收的很多细菌代谢产物对肝脏有伤害作用,然而越来越多的研究表明细菌产生的维生素K2对于肝脏具有保护作用。本文综述近几年来维生素K2在肝癌、肝硬化、肝再生等方面的研究进展,简要总结了维生素K2可能的作用机制,使我们看到了维生素K2防治肝脏疾病的潜力。     

Lapachol inhibition of vitamin K epoxide reductase and vitamin K quinone reductase

Lapachol [2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone] has been shown to be a potent inhibitor of both vitamin K epoxide reductase and the dithiothreitol-dependent vitamin K quinone reductase of rat liver microsomes in vitro. These observations explain the anticoagulant activity of lapachol previously observed in both rats and humans. Lapachol inhibition of the vitamin K epoxide and quinone reductases resembled coumarin anticoagulant inhibition, and was observed in normal strain but not in warfarin-resistant strain rat liver microsomes. This similarity of action suggests that the lactone functionality of the coumarins is not critical for their activity. The initial-velocity steady-state inhibition patterns for lapachol inhibition of the solubilized vitamin K epoxide reductase were consistent with tight binding of lapachol to the oxidized form of the enzyme, and somewhat lower affinity for the reduced form. It is proposed that lapachol assumes a 4-enol tautomeric structure similar to that of the 4-hydroxy coumarins. These structures are analogs of the postulated hydroxyvitamin K enolate intermediate bound to the oxidized form of the enzyme in the chemical reaction mechanism of vitamin K epoxide reductase, thus explaining their high affinity.     

Action of Solanum malacoxylon on calcium metabolism in the rat

The administration of an aqueous extract of the leaves from $\text{Solanum malacoxylon}$ to vitamin D-deficient rats fed a normal calcium, normal phosphorus diet markedly increased serum calcium concentration within 48 hours. The $\text{Solanum malacoxylon}$ extract also stimulated intestinal calcium transport in the vitamin D-deficient rat but was without effect on the mobilization of calcium from bone. The extract from 100 mg of dry $\text{Solanum malacoxylon}$ leaves was more effective than 25 units of vitamin D given daily to vitamin D-deficient rats in stimulating intestinal calcium transport but its effect was not additive to that of the vitamin D. The results demonstrate that the action of $\text{Solanum malacoxylon}$ is independent of vitamin D and, although it can substitute for vitamin D in the stimulation of intestinal calcium transport activity, it cannot substitute for vitamin D in the mobilization of calcium from bone.     

Vitamin K dependent in vitro production of prothrombin

During prothrombin biosynthesis, glutamyl residues in prothrombin precursor proteins are carboxylated to gamma-carboxyglutamyl residues by a vitamin K dependent carboxylase. Calcium-dependent and calcium-independent rat prothrombin antibody subpopulations have been produced and utilized to study the liver microsomal precursors of prothrombin that accumulate when vitamin K action is blocked. A substantial portion of the precursor pool accumulating in the vitamin K deficient or warfarin-treated rat will react with a Ca2+-dependent antibody at high calcium concentration and appears to be partially carboxylated. During in vitro incubation in the presence of vitamin K, the fraction of the precursor pool which is tightly bound to the microsomal membrane appears to be the preferred substrate for the vitamin K dependent carboxylation. A small amount of completely carboxylated rather than a large amount of partially carboxylated products are produced during these incubations. Treatment with a Sepharose-bound prothrombin antibody demonstrated that about 20-25% of the total carboxylated microsomal protein precursor pool consists of prothrombin precursors. This treatment removes an equal amount of total carboxylase activity, and the enzyme is active in this carboxylase precursor-antibody complex.     

The effect of vitamin E analogues and long hydrocarbon chain compounds on calcium-induced muscle damage. A novel role for α-tocopherol?

Previous studies have demonstrated that supplemental α-tocopherol inhibited calcium-induced cytosolic enzyme efflux from normal rat skeletal muscles incubated in vitro and suggested that the protective action was mediated by the phytyl chain of α-tocopherol [1]. In order to investigate this further a number of hydrocarbon chain analogues of tocopherol (7.8-dimethyl tocol, 5,7-dimethyl tocol, tocol, α-tocotrienol, α-tocopherol [10], vitamin K1, vitamin K1 [10], vitamin K1 diacetate, vitamin K2 [20], phytyl ubiquinone and retinol) were tested for any ability to inhibit calcium ionophore, A23187, induced creatine kinase (CK) enzyme efflux. Some compounds were found to be very effective inhibitors and comparison of their structures and ability and to inhibit TBARS production in muscle homogenates revealed that the effects did not appear related to antioxidant capacity or chromanol methyl groups, but rather the length and structure of the hydrocarbon chain was the important mediator of the effects seen.     

The effect of vitamin E analogues and long hydrocarbon chain compounds on calcium-induced muscle damage. A novel role for alpha-tocopherol?

Previous studies have demonstrated that supplemental alpha-tocopherol inhibited calcium-induced cytosolic enzyme efflux from normal rat skeletal muscles incubated in vitro and suggested that the protective action was mediated by the phytyl chain of alpha-tocopherol [1]. In order to investigate this further a number of hydrocarbon chain analogues of tocopherol (7,8-dimethyl tocol, 5,7-dimethyl tocol, tocol, alpha-tocotrienol, alpha-tocopherol [10], vitamin K1, vitamin K1 [10], vitamin K1 diacetate, vitamin K2 [20], phytyl ubiquinone and retinol) were tested for any ability to inhibit calcium ionophore, A23187, induced creatine kinase (CK) enzyme efflux. Some compounds were found to be very effective inhibitors and comparison of their structures and ability to inhibit TBARS production in muscle homogenates revealed that the effects did not appear related to antioxidant capacity or chromanol methyl groups, but rather the length and structure of the hydrocarbon chain was the important mediator of the effects seen.     

Vitamin D and chick embryonic yolk calcium mobilization: identification and regulation of expression of vitamin D-dependent Ca2(+)-binding protein, calbindin-D28K, in the yolk sac

The developing chick embryo acquires calcium from two sources. Until about Day 10 of incubation, the yolk is the only source; thereafter, calcium is also mobilized from the eggshell. We have previously shown that during normal chick embryonic development, vitamin D is involved in regulating yolk calcium mobilization, whereas vitamin K is required for eggshell calcium translocation by the chorioallantoic membrane. We have studied here the biochemical action of 1,25-dihydroxy vitamin D3 in the yolk sac by examining the expression and regulation of the cytosolic vitamin D-dependent calcium-binding protein, calbindin-D28K. Two types of embryos are used for this study, normal embryos developing in ovo and embryos maintained in long-term shell-less culture ex ovo, the latter being dependent solely on the yolk as their calcium source. Our findings are (1) calbindin-D28K is expressed in the embryonic yolk sac, detectable at incubation Days 9 and 14; (2) the embryonic yolk sac calbindin-D28K resembles that of the adult duodenum in both molecular weight (Mr 28,000) and isoelectric point, as well as the presence of E-F hand Ca2(+)-binding structural domains; (3) systemic calcium deficiency caused by shell-less culture of chick embryos results in enhanced expression of calbindin-D28K in the yolk sac during late development; (4) yolk sac calbindin-D28K expression is inducible by 1,25-dihydroxy vitamin D3 treatment in vivo and in vitro; and (5) immunohistochemistry revealed that yolk sac calbindin-D28K is localized exclusively to the cytoplasm of the yolk sac endoderm. These findings indicate that the chick embryonic yolk sac is a genuine target tissue of 1,25-dihydroxy vitamin D3.     

Direct stimulatory action of blood serum, vitamin D3, and its hydroxy-analogs on calcium transport in the small intestine of chicks in vitro

A study was made of the effect of blood serum, vitamin D3 and its hydroxy-analogs (25-hydroxyvitamin D4. 1 alpha-hydroxyvitamin D3) on Ca2+ transport across the wall of the noninverted small sac of D-avitaminosis chicken during incubation in vitro. It was shown that blood serum from chickens fed vitamin D3 in different doses (50--20 000 IU) and at varying time (1--72 h) before sacrifice produced a marked stimulating action on the cation transport 10 min after administration into the intestinal cavity as compared with the effect produced by the serum from D-avitaminosis chickens. Administration into the intestine of vitamin D3 or its hydroxy-analogs in physiological doses (6.25--25.0 ng) also significantly stimulated Ca+ transport over 10 min of incubation.     

Activity of antioxidants in serum of animals with experimental crush syndrome]

Ischemia of soft tissues in crush syndrome results in activation of free radical oxidation processes, which negatively effect the functions of many biological systems. The presence of antioxidant system in the body can inhibit the action of free radicals. Antiradical effect of this system is seen in vitamin K, ubiquinone and ascorbic acid. The results of the experiment showed that the quantity of vitamin K, ubiquinone and ascorbic acid increases in the serum of blood after decompression of soft tissues in 14 hours, three and seven days. This fact supports an active participation of antioxidant system in the pathogenesis of crush syndrome.     

Atypical Prothrombins induced by Dicoumarol

VITAMIN K maintains normal plasma prothrombin concentration. The effects of this vitamin as well as of its antagonist, dicoumarol, have been studied, often with the aid of inhibitors of protein synthesis, such as puromycin and cycloheximide^1–8. It is generally accepted that the site of action of vitamin K is not at the DNA level but at the late ribosomal stage; whether the vitamin acts in the de novo synthesis of prothrombin or in the completion of “unfinished” molecules is uncertain. Dicoumarol may cause release of unfinished material, or of “modified” molecules which are converted to the normal form by vitamin K. Conflicting evidence may be due to differences in dosage of protein inhibitors or of dicoumarol, differences in sampling time, differences in degree of purification, species variation, or differences in physical characteristics and chemical behaviour of unfinished or modified molecules which would demand that methods be specially adapted for their isolation.