Biosynthesis of factor V in isolated guinea pig megakaryocytes.

Chiu, Hui Chong; Schick, Paul K.; Colman, Robert W.

doi:10.1172/jci111706

Cited by 68 publications

(31 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…According to our bioassay the amount of factor V that is provided by the platelets in platelet-rich plasma is about 10% of the total factor V concentration. This value is somewhat lower than that reported by Tracy et al [15] and is in agreement with the findings of Chiu et al [16].…”

Section: Plasma F a C T O R V Activationsupporting

confidence: 93%

“…Immunological identity between platelet and plasma factor V has been shown in human species [15,17,18], bovine species [19, 201 and recently in guinea-pig between plasma factorV and a precursor form synthesized in the megakarocytes [16]. Whereas in the latter case functional differences were found after exposure to thrombin, in other reports the same quotient of activation by thrombin was found between platelet and plasma factor V [l, 21.…”

Section: Plasma F a C T O R V Activationmentioning

confidence: 90%

See 1 more Smart Citation

Kinetics of thrombin-induced release and activation of platelet factor V

1986

View full text Add to dashboard Cite

The kinetics of thrombin-induced platelet factor V activation were studied in suspension of washed human platelets. The effect of thrombin in stimulating the release reaction could be separated from its effect on factor V activation by use of a potent inhibitor of the release reaction, the prostacyclin analogue ZK 36374. When platelets were incubated with ZK 36374 prior to stimulation with thrombin, the amount of ZK 36374 required to inhibit 50% of factor V, formation was 15 pM. ZK36374 at a final concentration of 1 nM was found to block instantaneously and completely the release of factor V,, whereas it has no effect neither on platelet factor V activation nor on the factor V, assay. By varying the time interval between the addition of thrombin (0.5 nM) and ZK36374 to suspensions of 4.6 x lo6 platelets/ml the rate of factor V release was found to be 12 pM factor V/min. In the absence of ZK36374 the total amount of factor V released was 8 pM, whereas Triton X-100-treated platelets gave 13 pM factor V. It appeared that the amount of factor V that could be released was dependent on the thrombin concentration. Maximum release was obtained at 1 nM thrombin. The rate of factor V release increased in proportion to the thrombin concentration. The rate of factor V activation was found to be proportional to the thrombin concentration as well as to the amount of released factor V. When 4.6 x lo6 platelets/ml were activated by 0.5 nM thrombin, the rates of factor V activation were found to be 0.3 pM and 1.2 pM factor V,/min at 20% and 90% completion of the release reaction. Therefore, the rate of factor V release was at least one order of magnitude faster than the rate of factor V activation. The kinetics of thrombin-induced platelet factor V activation were compared to those of plasma factor V activation in platelet-rich and platelet-free plasma. The results clearly demonstrate that platelets have no effect on the rate of factor V activation and that the kinetics of plasma factor V activation are identical to those of platelet factor V activation.Thrombin-activated platelets are essential to the normal hemostatic mechanism. Two types of procoagulant activity from activated platelets have been recognized. In the first place factor V is released and activated during stimulation by thrombin [l, 21 and secondly the altered membrane of platelets activated by thrombin plus collagen provides a procoagulant surface [3, 41. These two events enable factor X, to function in a platelet-bound complex of factor V, and factor X,, the so-called prothrombinase, thus causing a dramatic amplification of the thrombin-generating capacity of factor X, [5, 61. Factor V occurs as a plasma protein as well as a protein present in the alpha granules of platelets.The question of the physiological importance of platelet factor V over plasma factor V in affecting the efficiency of the hemostatic process has been recently addressed by Tracy et al. [7]. These authors described an inherited factor V disorder and the association of a significant bleeding...

show abstract

Section: Plasma F a C T O R V Activationsupporting

confidence: 93%

Section: Plasma F a C T O R V Activationmentioning

confidence: 90%

Kinetics of thrombin-induced release and activation of platelet factor V

1986

View full text Add to dashboard Cite

show abstract

“…However, significant expression of FV in bone marrow/ bone is supported by previous studies, demonstrating a clear expression in bone marrow-derived megakaryocytes (16,17). Furthermore, recent bone marrow transplant models as well as transgenic mouse studies have demonstrated that the murine platelet FV pool is derived entirely from synthesis within bone marrow-derived megakaryocytes, while the circulating plasma FV pool is liver derived (15,18).…”

Section: Discussionmentioning

confidence: 83%

Estrogen increases coagulation factor V mRNA levels via both estrogen receptor-alpha and -beta in murine bone marrow/bone

Movérare

Skrtic

Lindberg

et al. 2004

European Journal of Endocrinology

View full text Add to dashboard Cite

Objectives: Both oral estrogen-based hormone-replacement therapy and contraceptives increase the risk of venous thromboembolism. Several circulating factors involved in coagulation/fibrinolysis are expressed mainly in the liver whilst some are expressed in extrahepatic tissues, including bone marrow. The aim of this study was to identify estrogen-responsive target genes involved in the pathogenesis of estrogen-induced venous thromboembolism. Methods: Ovariectomized mice were treated with 17b-estradiol and possible effects on the expression of genes related to coagulation/fibrinolysis were investigated using DNA microarray analyses. Results: None of the selected genes was regulated by 17b-estradiol in the liver. Interestingly, 17b-estradiol increased mRNA levels of coagulation factor V in the bone marrow/bone. Furthermore, this stimulatory effect of 17b-estradiol on coagulation factor V expression can be mediated via both estrogen receptor-a and -b. Conclusions: The expression of bone marrow-derived, but not liver-derived, coagulation factor V is increased by estrogen treatment in mice. The pathophysiological importance of this finding for estrogen-induced venous thromboembolism remains to be determined.

show abstract

“…Some a-granule proteins, such as platelet factor 4, appear to be synthesized only by megakaryocytes ( 1, 2, 8). Other a-granule proteins, such as fibrinogen (9,10), coagulation factor V (11,12), and von Willebrand factor (13), are synthesized by megakaryocytes in addition to other cell types. Serotonin, an amine synthesized mainly by enterochromaffin cells, is taken up and incorporated into dense granules by platelets and to a lesser extent by megakaryocytes (14,15).…”

Section: Resultsmentioning

confidence: 99%

Incorporation of a circulating protein into megakaryocyte and platelet granules.

Handagama¹,

George²,

Shuman³

et al. 1987

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

To determine whether or not proteins circulating in plasma can be incorporated into megakaryocytes and platelets, horseradish peroxidase (HRP) was injected intravenously into guinea pigs and these cells were examined for its uptake by electron microscopy and cytochemistry. Enriched samples of megakaryocytes enabled ultrastructural analysis of large numbers of these rare cells. In megakaryocytes, 50% of a granules contained HRP between 75 min and 7 hr after injection. At 24 hr, 25% of the megakaryocyte granules were peroxidase-positive, less were positive by 48 hr, and there were none at 4 days. Thus, the findings demonstrate that a circulating protein can be endocytosed by megakaryocytes and rapidly packaged into a granules. Platelet granules also contain HRP by 7 hr after injection, and they can secrete it in response to thrombin. Unfortunately, our present studies do not allow us to distinguish between direct endocytosis by the platelet and/or shedding of new platelets from recently labeled megakaryocytes. It is concluded that while some a granule proteins are synthesized by megakaryocytes, others may be acquired from plasma by endocytosis. In addition to providing evidence that some of the proteins of a granules may be of exogenous origin, this study has allowed the definition of a pathway whereby plasma proteins may be temporarily sequestered in megakaryocytes before reentering the circulation in platelets.One of the most striking characteristics of platelets is the large variety of proteins that are secreted during the release reaction. Platelets contain counterparts of several plasma proteins (albumin, fibrinogen, and others) in addition to platelet-specific proteins (platelet factor 4 and f3-thromboglobulin). These proteins are localized in a granules, the primary storage organelle for platelet secretory proteins. Predictably, many of these proteins have been shown to be synthesized in megakaryocytes, the bone marrow precursor cell from which platelets are derived. Platelet-specific proteins appear to be synthesized solely by megakaryocytes, whereas proteins such as fibrinogen, coagulation factor V, and von Willebrand factor are synthesized by other cell types in addition to megakaryocytes (1,2).Recently, we discovered that immunoglobulin G is located in platelet a granules and is secreted after platelet activation (3 In Vivo Studies. Male Hartley guinea pigs (300-400 g) were anesthetized with ether, and 75 mg of HRP was dissolved in 1 ml of physiologic saline and injected into the femoral vein. The animals were sacrificed with ether at short (15, 45, and 75 min) and long (7 hr, 24 hr, 48 hr, And 4 days) intervals after the injection. Blood was collected into acid/citrate/dextrose by heart puncture immediately before the guinea pigs were killed. Platelets were counted by use of an automated analyzer (Coulter S + IV). Platelet-rich plasma was obtained by centrifugation of the blood at 100 x g for 10 min at 22°C. Megakaryocytes were isolated from bone marrow according to a described technique (4), e...

show abstract

Biosynthesis of factor V in isolated guinea pig megakaryocytes.

Cited by 68 publications

References 25 publications

Kinetics of thrombin-induced release and activation of platelet factor V

Kinetics of thrombin-induced release and activation of platelet factor V

Estrogen increases coagulation factor V mRNA levels via both estrogen receptor-alpha and -beta in murine bone marrow/bone

Incorporation of a circulating protein into megakaryocyte and platelet granules.

Contact Info

Product

Resources

About