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Biomedical subjects

C Kluft

Publications and source records attributed to C Kluft.

At least 109 records · Page 6Linked to original sources
PubMed1996

Interindividual and intraindividual variability in plasma fibrinogen, TPA antigen, PAI activity, and CRP in healthy, young volunteers and patients with angina pectoris.

We compared intraindividual and interindividual variability in the plasma levels of fibrinogen, tissue-type plasminogen activator (TPA) antigen, plasminogen activator inhibitor (PAI) activity, and C-reactive protein (CRP) in 20 healthy, young individuals and 26 patients with stable angina pectoris (AP) who were at higher risk for cardiovascular disease. For each of the four parameters, the contribution of the intraindividual variation to the total variance (13% and 9% for fibrinogen, 3% and 5% for TPA antigen, 4% and 20% for In[PAI activity], and 14% and 9% for In[CRP] for the healthy volunteers and AP patients, respectively) was smaller than the contribution from the interindividual variation. These results indicate that single sampling is sufficient to assess an individual level for TPA antigen and PAI activity, whereas duplicate sampling for fibrinogen and triplicate sampling for CRP are recommended. In an epidemiological study the sample sizes, based on the variances found in the transverse part of the study, needed to detect a 15% difference between the two groups (with alpha = 0.01 and a statistical power = .90) are 31 and 40 for fibrinogen, 568 and 146 for TPA antigen, 603 and 119 for PAI activity, and 1490 and 2263 for CRP in healthy volunteers and patients with AP, respectively. Additionally, we studied the contribution of genetic polymorphisms of the B beta-fibrinogen (Bcl I and G-->A-455) and PAI activity (HindIII and CA-repeat) genes to intraindividual and interindividual variation. Fibrinogen genotypes were associated with plasma fibrinogen levels in the volunteers but not in the AP patients. No effects of fibrinogen or PAI polymorphisms on intraindividual variation were observed in either healthy individuals or AP patients. In this study intraindividual variation in plasma levels of the cardiovascular risk indicators fibrinogen, TPA antigen, PAI activity, and CRP was small when compared with the interindividual variation in healthy, young volunteers and patients with stable AP.

Adult↗
PubMed1996

Fibrin binding of plasminogen coated liposomes in vitro.

In this study, the fibrin binding properties of liposomes containing a number of plasminogen (Plg) molecules on the outside were compared to those of free (non-liposomal) Plg in an in vitro model system. Fibrin monolayer coated 96-wells plates were used, containing fibrin monomer at a density of around 3.4 to 3.9 x 10(-4) nmol/cm2. These densities are similar to liposomal Plg-densities, thus allowing multivalent interactions to occur. In the panel of experimental conditions that was chosen, binding of free Plg and liposomes with Plg showed three main differences in characteristics. Firstly, in the fibrin binding of Plg-liposomes not all Plg may be involved, but on the average 40% of the total amount of liposomal Plg. This was shown by lysing the liposomes after binding to the fibrin and estimation of truly bound Plg. With Plg-densities on the liposomes below the fibrin binding sites density, the maximal number of bound Plg molecules remains below the amount of available fibrin binding sites. Secondly, a higher binding rate by at least one order of magnitude was observed for liposomes with Plg compared to free Plg. Thirdly, liposomes with Plg exhibit a fibrin binding affinity which increases with Plg-density, because of the multivalent character of interaction. Liposomal Plg can successfully compete for fibrin binding sites with a 100 fold higher concentration of free Plg. These in vitro findings indicate that in view of avid and rapid fibrin binding, liposomes with attached plasminogen may be suitable for in vivo targeting to fibrin based thrombi.

Amino Acid Sequence↗
PubMed1996

Modulation of plasma fibrinogen levels by ticlopidine in healthy volunteers and patients with stable angina pectoris.

Elevated plasma fibrinogen levels are associated with an increased risk for cardiac events. Ticlopidine is a drug that inhibits the ADP-induced aggregation of blood platelets and it also has been described that ticlopidine can decrease the plasma fibrinogen level in patients with vascular diseases. The mechanism of this decrease has not yet been elucidated and therefore mechanisms that are known to affect fibrinogen levels were studied, viz, the acute phase reaction, total fibrin plus fibrinogen degradation (TDP) levels and the polymorphisms of the fibrinogen beta-gene. The fibrinogen lowering effect of ticlopidine was studied in 26 healthy volunteers, selected on genotype of the Bcl] polymorphism of the fibrinogen beta-gene, and in 26 patients with stable angina pectoris in a double blind, randomized cross-over study. Functional plasma fibrinogen levels were measured with the Clauss assay. Fibrinogen antigen, C-reactive protein (CRP) and TDP levels were measured using an enzyme immuno assay (EIA). In the healthy volunteers the functional fibrinogen levels had decreased by 0.20 g/l (9%, p = 0.005 using the paired Student l-test) after 4 weeks of 250 mg bid ticlopidine administration, whereas fibrinogen antigen, CRP and TDP levels were not significantly changed. In the stable angina pectoris patients the pre-treatment fibrinogen, CRP and TDP levels were significantly higher than in the volunteer group. After four weeks 250 mg bid ticlopidine administration the functional fibrinogen levels had decreased by 0.38 g/l (11%, p < 0.005), whereas the fibrinogen antigen, CRP and TDP levels were not significantly changed. The levels of functional and antigen fibrinogen, CRP and TDP did not change significantly during the placebo period in the volunteers or the patients. Neither in the volunteers nor in the patients was the effect of ticlopidine on the fibrinogen levels associated with the fibrinogen beta-gene polymorphisms. Therefore, the fibrinogen lowering effect of ticlopidine is likely to be a modulation of the functionality of the molecule and unlikely to be modulated by the acute phase reaction, TDP-levels or the fibrinogen beta-gene polymorphisms.

Adult↗
PubMed1995

Effect of low-dose heparin on urinary albumin excretion in insulin-dependent diabetes mellitus.

We investigated the effect of heparin on urinary albumin excretion in patients with insulin-dependent diabetes mellitus. 39 patients with persistent urinary albumin excretion of 30-300 mg/24 h were randomly treated for 3 months with subcutaneous injections twice daily of isotonic saline, 5000 IU unfractionated heparin, or 2000 anti-Xa IU low-molecular-weight heparin. Unfractionated and low-molecular-weight heparin induced a significant reduction in urinary albumin excretion (p = 0.04 and p = 0.004). The mechanism and clinical relevance is unknown but deserve further attention.

Adult↗
PubMed1995

Procoagulant activity and intimal dysfunction in IDDM.

The biological activity of thrombin and coagulation factor Xa was assessed in 62 insulin-dependent diabetic patients. A group of non-diabetic subjects of comparable age and urinary albumin excretion rate (< 30 mg/24 h) served as control subjects (group 1, n = 14). The patients were divided into three groups according to urinary albumin excretion rate. In group 2, albumin excretion rate was less than 30 mg/24 h (n = 17), in group 3 albumin excretion rate was in the range 30-300 mg/24 h (n = 20) and in group 4 albumin excretion rate was greater than 300 mg/24 h (n = 25). Compared to non-diabetic control subjects an increase in the biological activity of factor Xa was observed in all groups of diabetic patients (prothrombin fragment 1 + 2 levels were 1.14 +/- 0.38 nmol/l in group 2, p < 0.005; 1.06 +/- 0.45 nmol/l in group 3, p < 0.05 and 1.03 +/- 0.31 nmol/l in group 4, p < 0.05 vs 0.75 +/- 0.34 nmol/l in group 1). No difference in the level of antithrombin III was seen between the groups. We reconfirmed the presence of intimal dysfunction in diabetic nephropathy demonstrated by elevated transcapillary escape rate of albumin in group 4 compared with group 2 (8.9 +/- 2.0% vs 7.0 +/- 1.9%, p < 0.05). An overall positive correlation between transcapillary escape rate and prothrombin fragment 1 + 2 was found (r = 0.36, p < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Beneficial effect of a moderately energy-restricted diet on fibrinolytic factors in non-obese men.

Impaired fibrinolytic activity has been reported in the elderly and is thought to play a role in the etiology of cardiovascular disease, one of the leading causes of death in most Western countries. Since restriction of energy intake has been demonstrated to act beneficially on the aging process in a variety of species, we studied the effect of a 10-week moderately energy-restricted (ER) regimen (80% of habitual) on plasminogen activator inhibitor (PAI) activity, PAI-1 antigen, tissue plasminogen activator (tPA) activity, and tPA antigen in non-obese, middle-aged men. Moreover, the relationship between these fibrinolytic markers and glucose tolerance was investigated. Weight loss in the ER group (n = 16) was considerable (-7.4 +/- 1.7 kg, P < .001). Subjects in the control group (n = 8) also lost some weight (-2.1 +/- 1.5 kg, P < .01). Fasting glucose levels decreased in the ER group (-0.31 +/- 0.48 mmol/L, P < .05), which was correlated with the extent of weight loss (P < .01). Baseline insulin levels at 2 hours after an oral glucose load correlated with baseline PAI activity (P < .001) and PAI-1 antigen levels (P < .001). PAI activity decreased in the ER group (-2.94 +/- 2.90 IU/mL, P < .001), particularly in subjects with a high baseline PAI activity (> 9 IU/mL). Furthermore, energy restriction led to decreased PAI-1 antigen concentration (P < .05), a nonsignificant increase in tPA activity, and a decrease in tPA antigen concentration (P < .001). All these changes were more clear in subjects with a high baseline PAI activity. These results suggest that 10 weeks of moderate energy- restriction has a profibrinolytic effect in non-obese, middle-aged men, at least in subjects with higher baseline PAI activity (> 9 IU/mL). Moreover, in line with the suggestion that high PAI activity goes together with insulin resistance, a relationship between insulin concentration after a glucose load and PAI activity was found.

Adult↗
PubMed1995

Early spontaneous intermittent myocardial reperfusion during acute myocardial infarction is associated with augmented thrombogenic activity and less myocardial damage.

OBJECTIVES: This study investigated the influence of early spontaneous intermittent reperfusion on the extent of myocardial damage and its relation to endogenous hemostatic activity. BACKGROUND: In the early phase of acute myocardial infarction coronary occlusion is often intermittent, even before thrombolytic therapy is administered. The relation between this phenomenon, myocardial damage and hemostatic activity is unknown. METHODS: Holter ST segment recording and pretreatment plasma tissue-type plasminogen activator (t-PA) antigen, plasminogen activator inhibitor-1 (PAI-1) antigen, prothrombin fragment F1 + 2 and soluble fibrin levels were measured in 57 patients with acute evolving myocardial infarction. Spontaneous intermittent myocardial reperfusion, defined as two or more episodes of transient resolution of ST segment elevation to within 0.05 mV of baseline, lasting > or = 1 min, before the start of recombinant t-PA (rt-PA) treatment was present in 28 patients (group 1) and absent in 29 (group 2). Left ventriculography and coronary angiography were performed 90 min after intravenous rt-PA administration. Plasma creatine kinase-MB fraction (CK-MB) levels were measured every 6 h for 24 h, and C-reactive protein levels were measured daily for 3 days. RESULTS: Group 1 had lower peak plasma CK-MB (141.9 +/- 28.3 vs. 203.8 +/- 23.3 IU/liter [mean +/- SEM], p < 0.014) and C-reactive protein levels (16 +/- 4 vs. 28 +/- 4 mg/liter on day 1; 26.6 +/- 5.5 vs. 61.8 +/- 14.4 mg/liter on day 2; 19.6 +/- 4.2 vs. 40.6 +/- 6.5 mg/liter on day 3, p < 0.012) and a higher left ventricular ejection fraction (62.9 +/- 4% vs. 51.1 +/- 5%, p < 0.04) than group 2. Group 1 had lower plasma t-PA antigen levels (15.6 vs. 27 micrograms/liter, p < 0.006) but higher prothrombin fragment F1 + 2 (1.8 vs. 1.1 nmol/liter, p < 0.003) and soluble fibrin levels (66.8 vs. 31 nmol/liter, p < 0.01). Coronary patency at 90 min was similar. CONCLUSIONS: Early spontaneous intermittent reperfusion during acute myocardial infarction is associated with augmented thrombogenic activity and less subsequent myocardial damage. This finding is consistent with a protective effect of intermittency on the myocardium and a procoagulant effect of spontaneous lysis on blood. It may also reflect a different rate of evolution of coronary thrombosis and myocardial infarction in patients with and those without spontaneous intermittent myocardial reperfusion.

Analysis of Variance↗
PubMed1995

A specific allele of the histidine-rich glycoprotein (HRG) locus is linked with elevated plasma levels of HRG in a Dutch family with thrombosis.

Recent studies describe families with both elevated plasma HRG levels and thrombosis. In order to study the possibility that allelic variants of the HRG locus are associated with differences in HRG level, we studied linkage between HRG levels and a dinucleotide repeat polymorphism in a Dutch family which was selected on the presence of both thrombosis and elevated plasma HRG levels. No other known risk factors from thrombosis were found in this family. Linkage was calculated between the dinucleotide repeat and the HRG level considering the HRG level as a quantitative phenotype assuming a population prevalence of elevated HRG of 5%. Two classes of HRG levels were defined by a mean and a variance: one class with normal HRG levels and a second class with high HRG levels. Using a mean HRG level of 99% for individuals with a normal HRG level and 145% for individuals with high HRG, a maximum lod score of 4.17 (odds in favour of linkage of 22,000:1) was found at a recombination fraction of 0, indicating linkage. Considering the pedigree, an association was found between the presence of a specific allele (no. 6) of the dinucleotide repeat polymorphism and plasma HRG levels. Family members carrying allele 6 were found to have higher HRG plasma levels compared with family members lacking allele 6 (149% v 109% respectively). We conclude that in this family, linkage is found between the HRG locus and the HRG level, and that a HRG gene coupled to allele 6 of the dinucleotide polymorphism is associated with elevated plasma HRG levels. No evidence was found for a causal relationship between elevated plasma HRG levels and thrombosis in this family.

Aged↗
PubMed1995

Hyperhomocysteinaemia and endothelial dysfunction in young patients with peripheral arterial occlusive disease.

Hyperhomocysteinaemia, defined as an abnormally high plasma homocysteine concentration after an oral methionine load, is common in young (< or = 50 years) patients with peripheral arterial occlusive disease. It is thought to predispose to atherosclerosis by injuring the vascular endothelium. Treatment with pyridoxine and/or folic acid may lower plasma homocysteine levels. In mildly hyperhomocysteinaemic patients with peripheral arterial occlusive disease, we studied the effect of daily treatment with pyridoxine (250 mg) plus folic acid (5 mg) on homocysteine metabolism (i.e. plasma concentrations in the fasting state and after methionine loading, in 48 patients) and on endothelial function (in 18 patients). Endothelial function was estimated as the plasma concentrations of the endothelium-derived proteins, von Willebrand factor (vWF), thrombomodulin (TM), and tissue-type plasminogen activator (tPA). At baseline, fasting homocysteine levels were above normal in 24 of the 48 patients (50%); post-load levels, by definition, were above normal in 100% of patients. After 12 weeks of treatment, fasting and post-load levels were normal in 98 and 100% of patients, respectively. Endothelial function was assessed in 18 patients who completed 1 year of treatment. At baseline, median vWF (235%) and TM (57.1 ng mL-1) levels were above normal. At follow-up, vWF levels had decreased to 170% (P = 0.01) and TM levels had decreased to 49 ng mL-1 (P = 0.04). tPA levels were normal at baseline and did not change. Endothelial dysfunction is present in young patients with peripheral arterial occlusive disease and hyperhomocysteinaemia. Pyridoxine plus folic acid treatment normalizes homocysteine metabolism in virtually all patients, and appears to ameliorate endothelial dysfunction.

Adult↗
PubMed1995

Gender-related association between beta-fibrinogen genotype and plasma fibrinogen levels and linkage disequilibrium at the fibrinogen locus in Greenland Inuit.

Elevated plasma fibrinogen levels represent an increased risk for cardiovascular disease, but the mechanism explaining this association is still not clear. Genetic differences may play a role, because it has been shown that individuals who carry the rare alleles of polymorphisms in the genes for the B beta-chain (Bcl I and G/A-455) and the A alpha-chain (Taq I) of fibrinogen have higher plasma fibrinogen levels and that patients with peripheral arterial disease have a higher frequency of the rare allele of the Bcl I polymorphism than do healthy control subjects. We studied the Greenland Inuit, a population with a low incidence of ischemic heart disease; polymorphisms of the fibrinogen gene; and their association with plasma fibrinogen level. The group studied had a small age range (30 to 34 years), 97% were smokers, 62 were men, and 71 were women. We observed that in the Inuit, frequencies of the rare alleles of the beta gene and of the common alleles of the alpha gene polymorphisms were lower than those published for other populations (all Caucasian). Accordingly, in the Inuit, these distribution patterns give a higher frequency of alleles that are associated with lower plasma fibrinogen levels. We further observed comparable linkage disequilibrium between alpha and beta gene polymorphisms in Caucasian populations. In Inuit men the rare allele of the Bcl I and G/A-455 fibrinogen polymorphisms was associated with plasma fibrinogen level comparable with the association described in Caucasian populations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

The preparation of tissue-type Plasminogen Activator (t-PA) containing liposomes: entrapment efficiency and ultracentrifugation damage.

UNLABELLED: In this study, a method was developed for the efficient entrapment of active tissue-type Plasminogen Activator (t-PA) into liposomes. Experimental conditions were varied to optimize t-PA entrapment: different buffer solutions were used (pH 4 and 7.5), the effect of the incubation concentrations of phospholipid (PL) and t-PA was monitored and the influence of liposome-size was examined. Furthermore, the effect of ultracentrifugation on t-PA containing liposomes was determined in the presence and absence of Tween 80. t-PA entrapment strongly depended on experimental conditions and ranged from 30 up to 90%. Almost quantitative+ (90%) entrapment (entrapment percentage defined as absolute entrapment (IU t-PA/mumol PL) divided by total incubation ratio (IU t-PA/mumol PL), times 100%) was obtained in Hepes buffer pH 7.5, devoid of arginine, with low ionic strength. Ultracentrifugation, used for removal of non-entrapped t-PA, was shown to have a damaging effect on the liposomes (especially in the presence of 0.05% Tween 80), leading to t-PA loss. However, because acceptable alternatives were not available, ultracentrifugation was used during this study. Therefore, the encapsulation-percentage values shown in this study are in fact underestimates for the true entrapment of t-PA. IN CONCLUSION: almost quantitative t-PA entrapment in liposomes can be achieved by selecting the proper milieu and inducing a strong interaction between t-PA and bilayer.

Buffers↗
PubMed1995

Protection of single-chain urokinase-type plasminogen activator (scu-PA) in aprotinin treated cardiac surgical patients undergoing cardiopulmonary bypass.

Intraoperative high-dose aprotinin administration has been shown to reduce the intra-and postoperative blood loss in cardiac surgery. The haemostatic effect has been attributed to platelet preserving properties and to inhibition of contact activation reducing thrombotic and fibrinolytic activity during and after cardiopulmonary bypass (CPB). Here we report on the effects of aprotinin on urokinase-type plasminogen activator, especially on the protection of the zymogen single-chain urokinase-type plasminogen activator (scu-PA). scu-PA occurs cell associated as well as free in the circulation (concentration 50 pM, half-life 5 min), and is potentially activated by kallikrein and plasmin, both potent targets for aprotinin. The generated active two-chain u-PA (tcu-PA) is a powerful activator of fibrinolysis. Sixteen male patients undergoing myocardial revascularization were randomly assigned to aprotinin treatment (A) or control group (C). Plasma concentration of total u-PA antigen and of the specific forms scu-PA(zymogen) and tcu-PA(active enzyme) were measured at different stages intraoperatively and two hours postoperatively. After an initial drop due to haemodilution at the onset of CPB, the concentrations of circulating u-PA forms restored intraoperatively in A, but remained subnormal in C until the end of the observation period. The concentration of total u-PA antigen of shed mediastinal blood was both in A and C two-fold higher than in the circulation, but the antigen was preserved as the zymogen scu-PA in A and largely converted to an inactive, non activatable form in C. Intra- and postoperative blood losses were less than half the amount in A as compared to C.(ABSTRACT TRUNCATED AT 250 WORDS)

Aprotinin↗
PubMed1995

On the role of C1-inhibitor as inhibitor of tissue-type plasminogen activator in human plasma.

An enzyme immuno assay was developed to measure complexes of tissue-type plasminogen activator (t-PA) with C1-inhibitor in order to study the role of C1-inhibitor as an inhibitor of t-PA in plasma. In vitro experiments with melanoma and recombinant t-PA learned that purified C1-inhibitor reacts with both single chain t-PA and two chain t-PA. The rate constants ranged from 3.0 to 5.2 M-1s-1. In plasma, melanoma and recombinant two chain t-PA were hardly inhibited by C1-inhibitor, in contrast to melanoma and recombinant single chain t-PA which were inhibited to the same extent by endogenous C1-inhibitor as they were by purified C1-inhibitor. In vivo, t-PA/C1-inhibitor complex could be measured in plasma in a few cases in healthy volunteers (0.62 +/- 0.43 ng/ml t-PA equivalents), after exercise (0.84 +/- 0.25 ng/ml t-PA equivalents) and after a desmopression infusion (0.26 +/- 0.04 ng/ml t-PA equivalents). However, t-PA/C1-inhibitor complex was found in plasma in all cases after venous occlusion (1.7 +/- 0.5 ng/ml t-PA equivalents), in peritoneal fluid from patients suffering from peritoneal inflammatory disease (2.2 +/- 1.3 ng/ml t-PA equivalents) and in plasma from healthy volunteers during a t-PA infusion (27.7 +/- 18.5 ng/ml t-PA equivalents at peak level). In the last case, about 8% of the infused dose of recombinant t-PA (alteplase) was inhibited by C1-inhibitor at peak level.(ABSTRACT TRUNCATED AT 250 WORDS)

Complement C1 Inactivator Proteins↗
PubMed1995

Estrogens reduce plasma histidine-rich glycoprotein (HRG) levels in a dose-dependent way.

Plasma levels of histidine-rich glycoprotein (HRG) were investigated in three groups of women receiving a different dose of estrogens. First, the effect of low-dose estrogen was studied in a group of 83 postmenopausal women who were treated with 0.625 mg conjugated estrogens (CE). No significant change from baseline levels was found at the end of cycle 3 and cycle 13. Secondly, in 15 mothers and 23 daughters using oral contraceptives (OC) containing 30-50 micrograms ethinyl estradiol (EE) daily the mean HRG level was 14% and 24% lower than in a group of 144 mothers and 134 daughters not taking oral contraceptives, respectively (p < 0.05). Finally, in 11 excessively tall prepuberal girls who received 300 micrograms EE daily to reduce their final height the mean plasma HRG levels were decreased by 68% (p < 0.005). The effect of progestogens administered during low-dose and high-dose estrogen therapy appeared to be minor. The results from these three studies indicate that estrogens reduce plasma HRG levels in a dose-dependent way.

Adolescent↗
PubMed1995

Thrombolytic treatment with tissue-type plasminogen activator (t-PA) containing liposomes in rabbits: a comparison with free t-PA.

In this study, we aimed at improving the therapeutic index of tissue-type Plasminogen Activator (t-PA) as thrombolytic agent in the treatment of myocardial infarction. Liposome-encapsulated t-PA was tested in a rabbit jugular vein thrombosis model: administration of free t-PA (t-PA) as a bolus injection in the ear vein was compared to a similar administration of liposomal t-PA (t-PA-lip), liposomal t-PA in plasminogen-coated liposomes (Plg-t-PA-lip), a mixture of free t-PA and empty liposomes (t-PA+ empty lip) and a saline-blank (blank) in terms of thrombolytic activity and side effects. Liposomal t-PA (t-PA-lip/Plg-t-PA-lip) showed a significantly better thrombolysis efficiency than equimolar doses of free t-PA (t-PA/ t-PA+ empty lip): about 0.24 mg/kg of liposomal t-PA practically equalled the lysis-activity of a dose of free t-PA of 1.0 mg/kg (t-PA1mg/kg). On the other hand, liposome encapsulation did not affect the systemic activation of alpha 2-antiplasmin and plasminogen by t-PA. We conclude that for this model an improvement in thrombolytic efficacy of t-PA is achieved by liposome encapsulation of t-PA. As t-PA-lip and Plg-t-PA-lip -treatment induced similar results, targeting of liposomal t-PA by coupled glu-Plg remains a topic to be optimized in future studies.

Animals↗
PubMed1995

Identification and genetic analysis of a common molecular variant of histidine-rich glycoprotein with a difference of 2kD in apparent molecular weight.

Two forms of histidine-rich glycoprotein (HRG) were detected on SDS-PAGE by silver staining and immunoblotting after isolation of the protein from pooled plasma using immuno-affinity chromatography followed by chromatography with heparin-Sepharose. Both forms were single-chain molecules and the apparent molecular weights of form 1 and form 2 were 77 kD and 75 kD respectively. Mendelian inheritance of both HRG forms was observed in four families with 24 informative meioses, strongly suggesting that the two forms are encoded by different alleles. The frequency of form 1 and form 2 in a group of 36 individuals was 0.35 and 0.65 respectively. The difference between the two molecular variants was studied by direct sequence analysis of amplified exons of the HRG gene from 6 individuals who were homozygous either for form 1 or form 2. Five amino acid polymorphisms in three different exons were observed: Ile/Thr in exon4; Pro/Ser in exon 5; His/Arg, Arg/Cys and Asn/Ile in exon 7. Analysis of these polymorphisms in 20 volunteers showed that only the Pro/Ser polymorphism at position 186 in exon 5 was coupled to the form of the HRG protein. Ser was found in form 1 and Pro in form 2. The presence of Ser at position 186 introduces a consensus sequence for a N-glycosylation site (Asn-X-Ser/Thr). By removing N-linked sugars with N-glycanase, it could be demonstrated that the difference between the two forms of HRG is caused by an extra carbohydrate group at Asn 184 in form 1.

Amino Acid Sequence↗
PubMed1995

An amino acid polymorphism in histidine-rich glycoprotein (HRG) explains 59% of the variance in plasma HRG levels.

A pedigree-based maximum likelihood method developed by Lange et al. (12) was used to study the contribution of a newly defined di-allelic polymorphism in histidine-rich glycoprotein (HRG) to the plasma levels of HRG. In four families (n = 99) and 20 volunteers we found a heritability of 70%, an age effect of 3% and an effect of individual environmental factors of 27%. These results are remarkably similar to the results found in a previous parent-twin study in which a heritability of 69% and an effect of random environment of 31% was found. The overall genetic influence in the present study can be subdivided into an effect of 59% by the HRG phenotype and 11% by residual genetic factors. The influence of the HRG phenotype of 59% can entirely be explained by adding up the effect of the two alleles that make up the phenotype. These results indicate a codominant inheritance pattern of HRG levels in which the genetic influences can almost completely be ascribed to the additive effect of the di-allelic HRG locus whereas only a small part is due to other loci.

Alleles↗