[Glycosaminoglycans of the aorta in avitaminosis]

It has been shown that pregnancy specific beta 1-globulin (SBG) is found in the rat blood serum on the 6--7th day of pregnancy. SBG reaches the maximum by the end of pregnancy and is not detected already at the 3d--4th day after delivery. The placenta is the site of the SBG snythesis. Other organs of the pregnant rat are not able to incorporate radioactive aminoacids into the protein in vitro.

Studies on a subcellular system for vitamin K-dependent carboxylation

The subcellular localization of acarboxyprothrombin and the vitamin K-dependent carboxylation system has been studied using livers from vitamin K-deficient rats and found to be mainly in the membranes of the rough microsomal fraction. Bovine acarboxyprothrombin or fragment 1 thereof were inactive as substrates in the rat carboxylating system.

Nature of the vitamin K-dependent CO2 fixation in microsomal membranes

Vitamin K is a component of a membrane-bound enzyme complex which catalyzes the posttranslational carboxylation of peptide-bound glutamate to form the gamma-carboxyglutamate (Gla) residues of prothrombin. The reaction requires reduced vitamin K, bicarbonate, oxygen, and a carboxylase, and does not require ATP. In a Triton X-100 solubilized carboxylase system, it was found that the naphthoquinone ring structure is essential for activity, as is the 2-methyl group. Menaquinone homologs from MK-1 to MK-4 all had carboxylase activity, whereas menadione was inactive. However, dithiothreitol and other thiols form thioethers with menadione, which restores considerable carboxylation activity to the provitamin. Hydrogenation of the beta-gamma double bond in phylloquinone reduced its activity only slightly. The active species of "CO2" utilized in this carboxylation is CO2 and not bicarbonate. Ribosomes contain Gla residues and are labeled with CO2 when whole microsomes are incubated with CO2 in the presence of NADH and vitamin K. About 25% of the activity is releasable with puromycin, suggesting that Gla residues are formed on both the nascent chains and the structural proteins of ribosomes. The deoxycholate-solubilized carboxylase system can be dialyzed to yield membranous vesicles with enhanced carboxylase activity. The warfarin-binding protein from normal rats, but not that from warfarin-resistant rats, further enhances the carboxylase activity of these reformed vesicles.

[Metabolic indices in the connective tissue in experimental hyper- and hypovitaminosis K]

In experiments on rats the content of acid mucopolysaccharides (AMPS), collagen and elastin in a variety of the connective tissue--in the aorta of rats with hyper- and hypovitaminosis K was studied. In hypervitaminosis K no changes in the aortic wall were revealed. Hypovitaminosis produced by a special ration and pelentan was attended by a fall in the levels of AMPS and collagen. The elastin content reamained unchanged.

[Interaction of vitamins K and C in the body of rats]

The influence of ascorbic acid on the content and intracellular distribution of ubiquinone in the tissues of K-avitaminotic rats was investigated. Following introduction of pelentan (30--40 mg/kg), a vitamin K antagonist, a rise in the level of ubiquinone in all of the study organs, occurring both at the expense of the post-mitochondrial fraction of the liver, heart, spleen and also at that of the cardiac and splenic mitochondria, could be registered. The ubiquinone concentration in hepatic mitochondria was going down. In K-avitaminotic rats, which received ascorbic acid, the co-enzyme content in the tissues approached control values. Vitamin C exerted a positive action on the ubiquinone level in the mitochondria of the liver, heart and spleen. The cited data suggest that vitamin C abolishes manifestations of the K-vitamin deficiency affecting the ubiquinone pool and secures its optimal content in the mitochondria. Considering the significance of vitamins K, C and ubiquinone in the tissular redox processes an interaction of the said vitamins at the level of the tissue respiration chain is presumed.

[Role of vitamin K in glycoprotein metabolism]

The content of hexos-amines and proteins in glycoproteins (perchloric acid-soluble) of the liver and blood serum of rats following an excess administration of vitamin K (vikasol) and its antagonists--pelenten and large doses of sodium salicylate for a space of 15 days was studied. With hypovitaminosis K the content of glycoproteins in the liver and blood serum declines, while the ratio of the proteins and hexose-amines-- goes up. With its simultaneous administration with pelentan vikasol prevents the development of these changes.

[Collagen metabolism in the skin with different vitamin K regimens]

Secondary vitamin K deficiency in rats caused by pelentan was accompanied by a decrease in the total collagen content and a rise in free oxyproline in the skin. Under these conditions the rate of collagen hydrolysis proved to increase. Vitamin K (vikasol) prevented development of the mentioned shifts in collagen metabolism.

[Vitamins K and E and the functional state of connective tissue]

The function of the connective tissue in the skin of albino rats with the vitamin K deficiency was studied. Changes both in the cellular elements and in the fibrous structures (deranged differentiation of cellular elements, changes in the collagenformation, accumulation of acid mucopolysaccarides, etc.) were revealed. All of the mentioned changes are eliminated not only by introduction of vicasol, but also by that of alpha-tocopherol.

Effects of vitamin K deficiency, warfarin, and inhibitors of protein synthesis upon the plasma levels of vitamin K-dependent clotting factors in the chick

Two-week-old chicks adequate in vitamin K showed a relative lack of vitamin K-dependent clotting factors when compared with the rat, cow, and man. Chick prothrombin was 50%, IX 8%, and X 6% of respective levels in the rat. Factor VII was not detectable in chick plasma. When 1-day-old chicks were fed a vitamin K-deficient diet, prothrombin levels fell to 5% in 5 days, whereas factors IX and X fell to only 60% of normal. After warfarin administration to normal chicks, prothrombin levels fell to 20% in 6 hours, whereas factors IX and X fell to 60%. When cycloheximide was given to normal chicks, all vitamin K-dependent factors fell at the same relative rate with a half time of 2 hours. Cycloheximide also completely blocked the effect of physiological doses (10 mug) of phylloquinone upon prothrombin synthesis, but only partially blocked the effect of pharmacological doses (2.5 mg) of phylloquinone, suggesting an antagonism between cycloheximide and vitamin K at the ribosomal level. Puromycin was effective in blocking the action of vitamin K at both physiological and pharmacological doses. In the chick, unlike the rat, it appears that (1) cycloheximide is fully effective in blocking the action of physiological doses of vitamin K and (2) the regulatory systems for factors IX and X appear to have a higher affinity for vitamin K and a lower affinity for warfarin than the regulatory system for prothrombin.

A new carboxylation reaction. The vitamin K-dependent incorporation of H-14-CO3- into prothrombin

The bovine plasma zymogen prothrombin contains a number of gamma-carboxyglutamic acid residues which are not found in an abnormal prothrombin produced when cattle are given the vitamin K antagonist dicoumarol. These modified glutamic acid residues appear to be formed post-translationally by a reaction which requires vitamin K. It has been shown that postmitochondrial supernates from vitamin K-deficient rats incorporate added H-14-CO3- minus into microsomal proteins upon the addition of vitamin K. This incorporation is dependent upon the presence of the prothrombin precursor in the microsomal preparations, and upon factors which are present in the postmicrosomal supernatant. Most of the radioactive protein which can be obtained from the microsomal pellet by extraction with 0.25% Triton X-100 has been identified as prothrombin and it can be shown that all of the radioactivity is in the amino-terminal activation fragment of prothrombin. This portion of the protein has previously been shown to contain the gamma-carboxyglutamic acid residues. Hydrolysis of the purified radioactive prothrombin resulted in a loss of 50% of the radioactivity and subsequent chromatography of the amino acid hydrolyzate demonstrated that the remaining radioactivity was entirely in glutamic acid. These results are consistent with the hypothesis that all of the H-14-CO3- minus was incorporated into the carboxyl groups of gamma-carboxyglutamic acid residues.

Changes in phylloquinone epoxidase activity related to prothrombin synthesis and microsomal clotting activity in the rat

The oxidation of phylloquinone to the 2,3-epoxide (by phylloquinone epoxidase) was studied in liver from control and warfarin-resistant rats. The reaction requires microsomal fraction, soluble protein, a heat-stable soluble factor and O(2). It is not inhibited by CO or CN(-). Epoxidase activity was stimulated if plasma prothrombin was lowered either by anticoagulants or the absence of vitamin K. The activity of the enzyme rapidly returned to normal values after the administration of vitamin K to hypoprothrombinaemic rats. These differences in the activity of the enzyme occur in the microsomal fraction and not the cytosol. A thrombin-generating polypeptide that accumulates in microsomal fraction of hypothrombinaemic rats correlated directly with epoxidase activity. These data support the view that enzymic interconversion of phylloquinone and its 2,3-epoxide participates in the biological activity of vitamin K.