Problems in the measurement of zinc using heparin as an anticoagulant

Although several reports imply that anticoagulants and preservatives contain zinc, the quantity of zinc in heparin, if any, has not been documented. Zinc concentration was determined by flame atomic absorption spectroscopy in varying dilutions of multiple commercially obtained samples of purified sodium heparin N = 15 (microgram Zn/1000 Units heparin). Rubber stoppers of sterile heparin vials and of blood evacuation tubes were incubated in pre-analyzed water or saline on a mechanical shaker with fluid aliquots obtained up to 27 hours and analyzed for zinc content (microgram Zn/0.1 ml). Heparin, with contact or without contact with rubber stoppers, recorded identical zinc concentrations. Zinc concentrations varied from 0.222 +/- 0.01 (mean +/- SE) to 3.49 +/- 0.005 microgram Zn/1000 Units heparin. Leaching of zinc from rubber stoppers of vacutainer tubes (N = 9) was noted only with those containing known chelators of zinc. These results indicate that zinc is present in certain lots of sodium heparin and that caution must be exercised when reporting zinc concentrations of blood samples that contain sodium heparin as the anticoagulant.     

Influences of heparin on ACTH distribution and immunoreactivity in plasma of the rat. In vivo and in vitro studies

1. Blood samples from non-pregnant female rats were incubated in vitro with porcine 125I-ACTH, and the corresponding plasmas were chromatographed on fine Sephadex G 50. When heparin was added in vivo or in vitro, almost all the radioactivity appeared in the void volume of the columns; the same was observed when labelled ACTH was added to heparin-containing saline. In contrast, when NaCl instead of heparin was added to the blood in vivo as well as in vitro, almost all the plasma radioactivity was eluted later, with 125I-ACTH. 2. When labelled ACTH was i.v. administered to pregnant females, it was eluted in the void volume in the presence of heparin, and further down in its absence. 3. The same plasma samples from non-stressed or ether-stressed females were radioimmunoassayed for ACTH, with and without heparin. The degradation of ACTH was greater in the presence of heparin, and plasma ACTH concentration was understimated for low blood levels of heparin (5 UI/ml or less) and in contrast overestimated for high ones (25 or 50 UI/ml). 4. In conclusion, the reported data clearly demonstrated firstly that heparin added to rat blood traps ACTH molecules, promoting the formation of aggregates with apparent height molecular weight; secondly that heparin interferes with the direct radioimmunoassay of ACTH in the plasma.     

Flash chronopotentiometric sensing of the polyions protamine and heparin at ion-selective membranes

We report here on a highly sensitive and rapid detection technique, multipulse flash chronopotentiometry, for the anticoagulant polyion heparin and its antidote protamine. The technique is based on a localized titration of the polyions at the surface of an appropriately formulated polymeric ion-selective membrane devoid of ion exchange properties to prohibit spontaneous extraction processes. A defined ion flux from the sample side to the membrane is induced electrochemically by applying a current pulse of appropriate amplitude and sign. The resulting depletion of the measured ions at the membrane surface gives rise to a characteristic limiting current or transition time and is observed as an inflection point in the resulting chronopotentiogram. The limiting current and the square root of the transition time are linear functions of the concentration of the polyion and yield sensitive and rapid analytical information attractive for clinical diagnostics applications. The polyion protamine is detected in 10-fold diluted blood samples in a matter of seconds via a cathodic current pulse. The utility of the technique for monitoring heparin/protamine titrations in physiological saline solutions is demonstrated.     

Aqueous lithium heparin is a superior anticoagulant to solid heparin for blood collection from the retro-orbital sinus of rats

Blood specimens from the retro-orbital sinus of 80 Sprague Dawley rats were collected into tubes containing lithium heparin either as a solid or an aqueous solution. Plasma was separated for blood chemistry analysis. Twenty-eight blood specimens collected into tubes containing solid heparin were clotted and eight specimens were partially clotted making these samples unsuitable for some analyses. None of the specimens collected into heparin solution showed any evidence of clotting. The variances of lactate dehydrogenase and alpha-hydroxybutyrate dehydrogenase activities in plasma prepared with solid heparin were significantly greater than those prepared with heparin solution. Lithium heparin solution is now used routinely in our laboratory.     

Heparin and the heparin-precipitated human blood plasma fraction in the rosette formation reaction]

Experiments were conducted on CBA mice. The effect of heparin and of the fraction of human blood plasma precipitated by heparin (FPH) on the course of the specific immunity reaction, i.e. of rosette-formation, was studied. Inhibition of the mentioned reaction by FPH was revealed. No such effect was produced by heparin. Experiments were carried out in vitro. The results of the mentioned experiments were compared with literature data on the effect of heparin and FPH on other immunological reactions. A supposition was put forward that these substances interacting with lymphocytes had different points of application: heparin-cellular membrane, FPH-superficial cell receptors.     

Surface plasmon resonance sensor for heparin measurements in blood plasma

Surface plasmon resonance (SPR) was used as an affinity biosensor to determine absolute heparin concentrations in human blood plasma samples. Protamine and polyethylene imine (PEI) were evaluated as heparin affinity surfaces. Heparin adsorption onto protamine in blood plasma was specific with a lowest detection limit of 0.2 U/ml and a linear window of 0.2–2 U/ml. Although heparin adsorption onto PEI in buffer solution had indicated superior sensitivity to that on protamine, in blood plasma it was not specific for heparin and adsorbed plasma species to a steady-state equilibrium. By reducing the incubation time and diluting the plasma samples with buffer to 50%, the non-specific adsorption of plasma could be controlled and a PEI pre-treated with blood plasma could be used successfully for heparin determination. Heparin adsorption in 50% plasma was linear between 0.05 and 1 U/ml so that heparin plasma levels of 0.1–2 U/ml could be determined within a relative error of 11% and an accuracy of 0.05 U/ml.     

Development of an ISFET based heparin sensor using the ion-step measuring method

The ion-step measuring method was used to determine heparin concentrations in PBS and blood plasma. Heparin is a sulphated polysaccharide which is clinically used as a drug to prevent the clotting of blood. The measuring method is based on detection of changes in charge density in a porous membrane which is deposited on the gate of an ISFET. Protamine was used as affinity ligand in the membrane. In PBS a linear relation was found between the heparin concentration and the ISFET response. The incubation time was reduced from 18 h to 15 min by increasing the porosity of the membrane. The results of the measurements in blood plasma show a significant nonspecific binding of plasma components in the membrane. Suggestions are given to prevent this nonspecific adsorption. The results described in this paper show a detection limit for the ion-step measuring method of at least 5 ± 10⁻¹¹ Mol/l which is promising for future practical applications.     

Molecular mechanisms of the antiproliferative effect of beraprost, a prostacyclin agonist, in murine vascular smooth muscle cells

The antithrombotic activity of heparin has largely been credited with the success found in some cancer treatment by heparin. There are, however, many potent growth factors involved in tumor and blood vessel growth that bind to heparin with high affinity and their regulation by heparin may play a role in heparin's efficacy. We therefore chose to study the activity of a heparin analog, sucrose octasulfate (SOS), which has been similarly shown to interact with heparin-binding growth factors. Using mouse melanoma and lung carcinoma models, we demonstrate in vivo inhibition of tumor growth by SOS. SOS, however, showed little effect in coagulation assays indicating that this activity was not a primary mechanism of action for this molecule. Studies were then performed to assess the effect of SOS on basic fibroblast growth factor (FGF-2) activity, a growth factor which promotes tumor and blood vessel growth and is produced by B16 melanoma cells. SOS potently inhibited FGF-2 binding to endothelial cells and stripped pre-bound FGF-2 from cells. SOS also regulated FGF-2 stimulated proliferation. Further, SOS facilitated FGF-2 diffusion through Descemet's membrane, a heparan sulfate-rich basement membrane from the cornea, suggesting a possible role in FGF-2 clearance. Our results suggest that molecules such as SOS have the potential to remove growth factors from tumor microenvironments and the approach offers an attractive area for further study.     

Activity of natural fatty acids on erythrocyte osmotic resistance]

The aim of the present study was to assess the influence on the functional characteristics of the erythrocyte membrane of adding in vitro different natural fatty acids to blood taken from normal subjects. Blood samples were collected without stasis from healthy volunteers, anticoagulated with heparin or EDTA and incubated at 37 degrees C for 60 min with the different fatty acids at concentrations ranging between 1 x 10(-4) and 3 x 10(-2) molar. Two ml of blood were used for each test. The treated blood was added to graded solutions of NaCl (0.90-0.20 g/dl) at a ratio of 100 microliters/5 ml of solution. The suspensions were kept at room temperature and centrifuged for 10 min at 2000 g, in order to accelerate the sedimentation of the erythrocytes which had not been broken down and so as to obtain a clear supernatant for spectrophotometry of the dissolved haemoglobin. Readings were compared with those obtained from blood samples which had been completely haemolyzed by suspension in distilled water. Results obtained with the blood samples prepared with the fatty acids were compared with control samples from the same donor, also incubated at 37 degrees C for 60 min. Preincubation of the erythrocyte with butyric or caproic or oleic acid at concentrations ranging between 5 and 20 millimolar, provoked a clear deterioration of the osmotic resistances of the erythrocytes, in proportion to the concentration of the fatty acid used. The osmotic insult was systematically more effective in those samples anticoagulated with EDTA than those treated with heparin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Titrimetric method for determination of O-desulfated heparin in physiological samples using protamine-sensitive membrane electrode as endpoint detector

O-Desulfated heparin (ODSH) is a promising new anti-inflammatory agent for the prevention of reperfusion injury following myocardial infarction or stroke. This partially desulfated heparin derivative has less anticoagulant activity than unfractionated heparin but retains the inherent anti-inflammatory properties of heparin. Thus, ODSH could be administered at the high doses needed to achieve desired anti-inflammatory function without risk of hemorrhage. However, given the very low anticoagulant activity of this species, traditional methods for heparin determination in clinical samples might not be well suited for ODSH measurements. In this article, a novel titrimetric method for detection of ODSH in buffer and plasma is described using a protamine-sensitive polymer membrane electrode as the detector. Titrations of ODSH with the heparin antagonist protamine yield sharp endpoints with sensitivity to ODSH in the micrograms per milliliter range for plasma samples. The stoichiometry for protamine interaction with ODSH is determined to average 1.39 microg protamine/microg ODSH in plasma. This technology is further applied to a toxicokinetic study of ODSH in an animal model, demonstrating the ability to detect the changes in ODSH concentrations in biological samples.     

Correlated measurement of platelet release and aggregation in whole blood

We have used a technique for the simultaneous measurement of platelet activation and aggregation in whole blood using two-color immunofluorescence and flow cytometry to study the relationship between the release reaction and aggregation. A monoclonal antibody specific for the alpha granule membrane protein GMP-140 was used to measure the release reaction, and a monoclonal antibody specific for platelet membrane glycoprotein Ib (GPIb) was used to identify platelets and platelet aggregates. Aggregates were identified as particles expressing both levels of GPIb and size larger than that of resting single platelets. Anticoagulated whole blood was incubated with platelet agonists. At various times samples of the blood were removed and immediately fixed with paraformaldehyde. Blood that had been anticoagulated with ethylenediamine tetraacetic acid showed progressive release of platelets but little or no aggregation. However, blood anticoagulated with citrate or heparin showed correlated release and aggregation. The degree of aggregation was greater in heparin than in citrate. The expression of GPIb and GMP-140 increased in direct proportion to the size of the aggregates. Aggregates were observed varying in apparent diameter up to approximately 20 microns. During prolonged incubation there was progressive disaggregation of adenosine diphosphate (ADP)-induced aggregates. After disaggregation the proportion of GMP-140 negative single platelets increased, indicating that both released and nonreleased platelets participated in the aggregation. There was little or no disaggregation of phorbol myristate acetate (PMA)-induced aggregates. The relatively small size and reversibility of platelet aggregates that we have observed in whole blood may be relevant to phenomena occurring in vivo and in extracorporeal circulation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Heparin as a Therapy for Atherosclerosis: Preliminary Observations on the Intrapulmonary Administration of Low-Dose Heparin in the Morning Versus Evening Gauged by Its Effect on Blood Variables

Reports on clinical trials with subcutaneous and intrapulmonary administration of low-dose heparin suggest that it may be an attractive therapeutic modality for the treatment of coronary artery disease because of unprecedented reduction in mortality of treated subjects. As a preliminary to a clinical trial with low-dose intrapulmonary heparin, a pilot study was conducted on three subjects. It compares overall circadian responses of 37 blood variables following intrapulmonary administration of heparin (10,500-18,800 U) in the morning (0800 h) and in the evening (2000 h). After each of these times, blood samples, mostly at 3 h intervals for the ensuing 27 h, were analyzed for heparin, APTT, TT, functional fibrinogen, CBC, enzymes, lipids, electrolytes, and hormones. Each time series was analyzed for circadian rhythm by the least-squares fit of a 24 h cosine and circadian mesors were compared by the Bingham test of rhythm parameters. Following heparin in the evening, but not in the morning, a statistically significant increase in circulating heparin levels, as well as directional increases in APTT and TT and decreases in fibrinogen, were observed in all three subjects. Same direction changes in several other variables were also observed. It is concluded that inhalation of heparin in low-dose levels results in variable circadian effects on blood parameters measured, ranging from no changes in their levels to minimal within normal range changes, and that these effects are dependent upon the timing of dose administration. It is suggested that the timed self-administration of low-dose heparin by inhalation be seriously considered for long-term clinical trials in the treatment and prevention of atherosclerosis.     

Effect of heparin on the reactivity of SH-groups in the macrophage membrane

The effect of heparin on macrophage (M phi) adherence and on the reactivity of membrane SH-groups to the specific SH-oxidizing agent 4,4'-dithiodipyridine (PDS) was studied. Various types of SH-reactive agents, except 5,5'-dithio-bis (2-nitrobenzoate) (DTNB), were found to inhibit adherence of mouse peritoneal M phi to serum-coated Falcon surfaces. Heparin inhibited M phi-adherence in serum containing medium and in higher concentrations stimulated the adherence inhibitory effect of PDS, especially in Ca-depleted medium. This effect of heparin may be due to its polyanionic character, as dextran sulphate but not dextran induced similar changes. The effect of heparin to increase the sensitivity of membrane SH-groups against SH-reactive agents was demonstrated also by cytotoxicity experiments. It is concluded that heparin makes the M phi-membrane unstable, by exposing some hidden SH-groups playing a role in membrane function.     

Role of heparin in the realization of the hypoglycemic action of insulin

The presence of reactive heparin in blood circulation is necessary for realization of the hypoglycemic action of insulin. This is confirmed by the fact that after heparin binding by protamin sulfate both endogenous and exogenous insulin do not exhibit any hypoglycemic activity. In animals with different basal concentration of heparin in the blood, the blockade of insulin action is attained by application of different doses of protamin sulfate, respectively. Based on the data obtained one can determine an approximate blood heparin concentration necessary for realization of the hypoglycemic action of insulin.     

Heparin as a Therapy for Atherosclerosis: Preliminary Observations on the Intrapulmonary Administration of Low-Dose Heparin in the Morning Versus Evening Gauged by Its Effect on Blood Variables

Reports on clinical trials with subcutaneous and intrapulmonary administration of low-dose heparin suggest that it may be an attractive therapeutic modality for the treatment of coronary artery disease because of unprecedented reduction in mortality of treated subjects. As a preliminary to a clinical trial with low-dose intrapulmonary heparin, a pilot study was conducted on three subjects. It compares overall circadian responses of 37 blood variables following intrapulmonary administration of heparin (10,500-18,800 U) in the morning (0800 h) and in the evening (2000 h). After each of these times, blood samples, mostly at 3 h intervals for the ensuing 27 h, were analyzed for heparin, APTT, TT, functional fibrinogen, CBC, enzymes, lipids, electrolytes, and hormones. Each time series was analyzed for circadian rhythm by the least-squares fit of a 24 h cosine and circadian mesors were compared by the Bingham test of rhythm parameters. Following heparin in the evening, but not in the morning, a statistically significant increase in circulating heparin levels, as well as directional increases in APTT and TT and decreases in fibrinogen, were observed in all three subjects. Same direction changes in several other variables were also observed. It is concluded that inhalation of heparin in low-dose levels results in variable circadian effects on blood parameters measured, ranging from no changes in their levels to minimal within normal range changes, and that these effects are dependent upon the timing of dose administration. It is suggested that the timed self-administration of low-dose heparin by inhalation be seriously considered for long-term clinical trials in the treatment and prevention of atherosclerosis.     

Interpretation of the mechanism of changes in electrophoretic motility after exposure to physical fields in a solid liquid mosaic model of the erythrocyte

A decrease of electrophoretic mobility of the blood red cell under the influence of the microwave and thermal field is determined by the mechanism based on two effects--change of the ionic conductivity and visco-elastic properties of the membrane.     

Effects of exogenous heparin on the vasculogenesis of the chorioallantoic membrane

On the basis of the well-known stimulating role played by heparin on blood vessel neoformation in the chorioallantoic membrane (CAM), demonstrated by means of slow-release polymers soaked in this substance and placed on CAMs, a new technique of introducing heparin directly into the allantoic sac is proposed. According to observations carried out in ovo and after fixation, morphological modifications are demonstrated in the developing vasculature of the heparin-treated CAMs which, compared with the control CAMs, show dilated and sinuous arterial and venous branches, denser and irregular capillary networks, and a high number of vascular primordia. The results, confirming that heparin is involved in angiogenesis, indicate the suitability of the technique and suggest that the effects of this substance could be enhanced by growth factors released by CAM tissues rapidly growing up from the 5th to the 7th incubation day.     

Platelet function in stored heparinised autologous blood is not superior to in patient platelet function during routine cardiopulmonary bypass

Background

In cardiac surgery, cardiopulmonary bypass (CPB) and unfractionated heparin have negative effects on blood platelet function. In acute normovolemic haemodilution autologous unfractionated heparinised blood is stored ex-vivo and retransfused at the end of the procedure to reduce (allogeneic) transfusion requirements. In this observational study we assessed whether platelet function is better preserved in ex vivo stored autologous blood compared to platelet function in the patient during CPB.

Methodology/Principal Finding

We measured platelet aggregation responses pre-CPB, 5 min after the start of CPB, at the end of CPB, and after unfractionated heparin reversal, using multiple electrode aggregometry (Multiplate®) with adenosine diphosphate (ADP), thrombin receptor activating peptide (TRAP) and ristocetin activated test cells. We compared blood samples taken from the patient with samples taken from 100 ml ex-vivo stored blood, which we took to mimick blood storage during normovolemic haemodilution. Platelet function declined both in ex-vivo stored blood as well as in blood taken from the patient. At the end of CPB there were no differences in platelet aggregation responses between samples from the ex vivo stored blood and the patient.

Conclusion/Significance

Ex vivo preservation of autologous blood in unfractionated heparin does not seem to be profitable to preserve platelet function.     

Heparin, lipoproteins, and oxygenated fatty acids in blood: a cautionary note

We measured 16 nonesterified oxygenated fatty acid derivatives (oxylipids) in plasmas from seven human subjects. Two arterial samples from each subject were analyzed, drawn approximately 2h apart. We observed a marked increase in levels of most oxylipids in the second sample, as high as 470-fold. Between the first and second samples, subjects received approximately 800-1000 IU of heparin to prevent clotting in intravascular catheters. We postulate that heparin activated lipoprotein lipases, which, in turn, released oxylipids from triglycerides and phospholipids in plasma lipoproteins. Some of that lipolysis may have occurred during sample storage. Measurements of nonesterified lipids in human plasma may be distorted if heparin is administered to subjects before blood is drawn and if lipase inhibitors are omitted from stored samples.