Platelet Production Rate Research Articles

Inhibition of Platelet Production Induced by an Antiplatelet Drug, Anagrelide, in Normal Volunteers

Administration of anagrelide, an antiplatelet agent, to ten normal male subjects was accompanied by an asymptomatic fall in platelet count. The drop was gradual and usually occurred within two weeks. Only a slight shortening of platelet survival was seen. Bone marrow morphology appeared normal. Measurement of platelet production rates showed a reduced response to thrombocytopenia. A substantial increase in the percentage of large platelets was observed in drug treated subjects. These observations are compatible with a selective inhibition of platelet production. Based upon these findings, the use of anagrelide will probably be best limited to short-term applications or to conditions where selective lowering of platelet count may be desired such as in polycythemia rubra vera or idiopathic thrombocytosis.

75Se-Seleno-Methionine-Actin as a Probe for Determination of Platelet Production Rate

Synthesis of actin is a reasonably correct representation of the platelet production rate. Measurement of actin production obviates some of the drawbacks encountered in currently available methods. Platelet actin was characterized on polyacrylamide gel electrophoreses using methylated radioactive rabbit actin as a reference. Platelet actin was unambiguously identified by showing that it forms a complex with DNAase-I similar to the complex obtained with pure rabbit actin. Six days after intravenous injection of 75Se-seleno-methionine actin was one of the most highly labelled platelet components. The platelet pellet (one rat per sample) was solubilized with 1% Triton X-100, 0.75 M guanidine-HCl and dialyzed in a medium containing 1% SDS (to eliminate Triton X-100 and guanidine-HCl). A carefully measured aliquot was deposited on a polyacrylamide gel. After electrophoresis in the presence of SDS the radioactivity of the actin band was measured and the ratio of the total actin radioactivity to the injected radioactivity was taken as a measure of platelet production. The validity of the actin probe was tested with populations of normal animals. The specific radioactivity of actin was proportional to the injected dose of 75Se-seleno-methionine up to 1 mCi/kg animal. A semi-log plot of actin specific radioactivity vs time exhibited a pseudo-first order decrease. Another constituent with a high specific radioactivity (XM) was excluded as a suitable probe because it was shown to be an adsorbed plasma protein.

Acquired haemostatic defects in the ill newborn.

Summary. The kinetics and function of platelets and fibrinogen were studied in 22 ill newborns. Overall 51Cr‐platelet survival was considerably shortened (patients 2·6 d ± 1·7, adult normal 9·5 d ± 0·6, P < 0·001) while 125I‐fibrinogen surival was less severely decreased (patients 2·1 d ± 0·8, adult normal 5·1 d ± 0·4, P < 0·05).Three patients with bacterial sepsis and one with disseminated herpes simplex had the most severely reduced platelet survival times (1·3 d ± 0·9), causing thrombocytopenia (62 ±32 × 109/l) despite production rates averaging 2 1/2 times normal. Although fibrinogen survival times were comparably reduced in these patients to 1·4 d ± 0·4, fibrinogen concentrations were normal because of compensatory increased production.In three patients with necrotizing enterocolitis platelet and fibrinogen survival times were similarly reduced (platelets 1·6 d ± 0·6, fibrinogen 1·6 d ± 0·6) with platelet counts of 69 ± 27 × 109/l and platelet production rates of twice normal. Since their fibrinogen production was not increased, they had decreased fibrinogen concentration (1·0 ± 0·19 g/l).In six patients with respiratory distress syndrome the kinetic results were more variable. Platelet survival was less severely affected than in the other groups and production was approximately twice normal; hence, the platelet count was maintained (177 ± 107 × 109/l). Fibrinogen in this group was slightly reduced because of decreased production in the presence of mildly decreased survival (2·7 d ± 0·7).The two patients with cytomegalovirus infection had severe thrombocytopenia (23 × 109/l) due to a combination of decreased platelet survival (3·6 d), increased splenic pooling and no compensatory increase in marrow platelet production. Fibrinogen production was normal but its plasma concentration was moderately reduced because of a decrease in fibrinogen survival.In many of these patients, fibrinogen dysfunction was suggested by a prolonged thrombin time and a discrepancy between fibrinogen concentration as determined by a time dependent assay and an equilibrium total clottable protein assay. Likewise, platelet dysfunction, evidenced as a prolonged bleeding time, was found in patients with RDS; some of these infants had otherwise unexplained bleeding.

The relation of platelet kinetics to bone marrow megakaryocytes in chronic granulocytic leukaemia.

The relation of thrombokinetics to quantitative determinations of megakaryocytes (mgkc) in bone marrow sections was studied in 11 consecutive cases of untreated Ph1-positive chronic granulocytic leukaemia (CGL). The results were compared with controls and with previously obtained data in polycythaemia vera (PV), primary thrombocythaemia (PT) and in idiopathic thrombocytopenic purpura (ITP). Platelet survival was significantly reduced in CGL. Platelet production was 5.8 x normal and the mgkc number and volume/microliter bone marrow were significantly increased as compared to controls. The increase in mgkc volume was not in proportion to that of number due to a significant decrease of mgkc size. Platelet production was strongly related to mgkc number/mm2 and to the mgkc volume/microliter bone marrow. The platelet production rate in relation to a unit of mgkc volume/microliter bone marrow was, however, greater in CGL than in controls, PV, PT and ITP. The chief reason for this is most probably the greater expansion of the total bone marrow mass in CGL.

Bone marrow megakaryocytes and platelet kinetics in systemic lupus erythematosus. With special reference to corticosteroid and azathioprine therapy.

The megakaryocyte number and mean megakaryocyte area were determined in histological sections of sternal bone marrow from 26 patients with systemic lupus erythematosus (SLE). Also 20 platelet survival studies were carried out in these patients. The results were analyzed with respect to corticosteroid (CS) and CS + azathioprine (AT) therapy. The mean bone marrow megakaryocyte number as highest in untreated SLE patients, slightly lower in patients receiving CSs and lowest in those receiving CSs + AT. The difference was, however, not significant. The mean megakaryocyte areas were smallest in untreated SLE patients, slightly larger in those treated with CSs and significantly (p less than 0.05) larger in patients who received CSs + AT than in untreated patients. Platelet production rate was normal in all 3 groups of SLE patients. The results suggest that CS and AT therapy in SLE intervenes with the bone marrow megakaryopoiesis without affecting the production rate of platelets.

Measurement of thrombocytopoiesis in W/Wv mice with evidence for an abnormality of sulfate metabolism.

Mice of the W/W/sup v/ genotype have an hereditary macrocytic anemia resulting from a diminished proliferative capacity of hemopoietic precursor cells. Platelet production was studied because W/W/sup v/ mice maintain a normal number of circulating platelets that are of methionine and calculating the percentage of the injected dose incorporated by platelets, the platelet production rate of W/W/sup v/ mice was found to be equivalent to the production rate of their +/+ littermates. Using NA/sub 2//sup 35/SO/sub 4/, however, the platelet production rate, as measured by the same isotope incorporation method, was nearly twice the rate of the normal littermates. The increase in /sup 35/S incorporation appeared to be explained by a greater availability of isotope in the W/W/sup v/ as evidenced by the higher plasma levels of /sup 35/S that were concurrently found. This suggests that the W/W/sup v/ mouse has an aberrant metabolism of inorganic sulfate probably unrelated to platelet production. These results also demonstrate how failure to take plasma radioactivity levels into account can lead to conflicting and probably erroneous conclusions in animals with an inherent or induced metabolic abnormality.

Platelet kinetics in systemic lupus erythematosus (SLE), with special reference to corticosteroid and azathioprine therapy.

Duplicate platelet survival studies were carried out on 10 patients with SLE. At the time of the first study 5 of them (group I) were untreated and the remaining 5 (group II) were receiving corticosteroid (CS) therapy. The second study was performed while group I patients received CS and group II patients CS + azathioprine (AT) treatment. Untreated SLE patients were shown to have normal values for platelet mean life-span (MLS) and platelet production rate. CS and AT treatment did not affect either platelet MLS or platelet production rate. The present study also provides further evidence that a state of compensated thrombocytolysis is not present in SLE.

Platelet survival and platelet production in systemic lupus erythematosus (SLE).

Platelet survival studies were carried out on 36 patients suffering from SLE. Twelve of them received no therapy, 17 were on corticosteroids (CS), and the remaining 7 received CS and azathioprin (AT). Ten healthy hospital employees served as controls. Only 1 of our SLE patients had thrombocytopenia (platelet count 42 x 10(9)/l). All the remaining 35 patients had venous platelet counts greater than or equal to 120 x 10(9)l. In the control group the average platelet mean life-span (MLS) was 5.8 +/- 0.3 (range 4.0-6.8) days. In the group of untreated SLE patients 3 out of 12 subjects (25%) had a platelet MLS below the lower range for the controls. The mean platelet MLS in the control group did not differ statistically from any of the means of the three groups of SLE patients studied. The lowest mean for platelet MLS (5.2 +/- 0.6 days) was encountered in the group of patients who received no therapy. The means for platelet MLS in the two groups of SLE patients who received immunosuppressive therapy were higher (6.5 +/- 0.4 and 6.6 +/- 0.4 days, respectively) but did not differ statistically from the mean of untreated patients (0.10 > p > 0.05). The mean platelet production rate in the control group (23 +/- 10(10) platelets per day) did not differ from any of the three groups of SLE patients investigated. In the literature it has been proposed that a state of compensated thrombocytolysis is present in most cases of SLE. The results of the present study do not support this hypothesis, however.

Thrombokinetics in giant cell arteritis, with special reference to corticosteroid therapy.

Duplicate platelet survival studies were carried out on 8 patients with giant cell arteritis (GCA), once before the institution of any therapy, and the second time when they were in a completely asymptomatic phase after having received corticosteroid treatment. The time interval between the studies ranged between 5 and 14 months. In the first study the mean peripheral platelet count was 486 +/- 25 X 10(9)/l and in the second 326 +/- 25 X 10(9)/l. The difference between the means was highly significant (P less than 0.001). The mean life-span of the platelets was normal in the duplicate experiments (6.7 +/- 0.3 and 7.3 +/- 0.4 days, respectively). Platelet production rate was significantly (P less than 0.001) raised in the first experiment but became normal in response to corticosteroid therapy. It is concluded that the thrombocytosis seen in GCA is reactive to the inflammation present in this disease, and it seems reasonable to assume that the reduction in the peripheral platelet count which occurs in response to corticosteroid therapy accurately reflects the clinical improvement of the patient.

Long‐Term Plateletpheresis in the Management of Primary Thrombocytosis

We attempted to control the platelet count of a patient with primary thrombocytosis utilizing long-term plateletpheresis therapy. The patient previously could not be controlled with chemotherapy, because of rapid development of leukopenia. Although intensive pheresis at the rate of four to five procedures per week produced rapid lowering of the patient's platelet count, continued therapy at the rate of two to three procedures a week failed to maintain these counts, and platelets gradually rose to pretreatment levels. We conclude that while plateletpheresis can produce acute lowering of elevated platelet counts, the rate of platelet production in primary thrombocytosis may be too rapid to allow for long-term control by pheresis alone, utilizing an acceptable treatment schedule of one of three procedures per week.

Effects of thrombopoietin and erythropoietin on platelet production in rebound-thrombocytotic and normal mice.

AbstractThe effects of thrombopoietin‐rich (TSF‐rich) kidney cell culture medium and partially purified preparations of human urinary and step I sheep plasma erythropoietin (Ep) on platelet production in mice were determined. After TSF and Ep preparations had been injected into mice in rebound thrombocytosis and into normal mice, the rate of incorporation of Na2 35SO4 into platelets was measured as an index of platelet production. TSF injections caused significant increases in platelet production of all the mice; however, greater effects were observed in rebound‐thrombocytotic mice than in normal mice. In rebound‐thrombocytotic mice, low dosages of Ep (0.25–1.0 units per mouse) significantly depressed percentage 35S incorporation into platelets. The same low dosage of Ep did not alter platelet production rates in normal mice, but large doses (2.5–5.0 units per mouse) stimulated 35S incorporation into platelets. Thus, these results show that Ep caused different responses in rebound‐thrombocytotic and normal mice. Endotoxin, injected in dosages previously shown to be present in Ep, gave responses similar to that of the low dosages of Ep, ie, depressed thrombocytopoiesis in rebound‐thrombocytotic mice but had no effect in normal mice. When two foreign proteins were injected in doses similar to the previously tested Ep protein content, platelet production was not stimulated. We conclude, therefore, that the thrombocytopoietic effects of Ep cannot be due to contamination with known humoral factors or foreign proteins.

Platelet Survival and Platelet Production in Acute Myocardial Infarction

Thrombokinetic studies were carried out on 26 consecutive patients with myocardial infarction (MI) admitted to a coronary care unit in the acute stage during a two-month period. The results were compared with those of an age-matched control group. In the MI patients, platelet mean life-span was 5.0 +/- 0.3 days and significantly shorter (p greater than 0.01) than in the controls (6.4 +/- 0.4 days). The mean platelet production rate for the patients with MI was significantly higher (p greater than 0.005) than for the controls. On the basis of results reported by others as well as the present data, it is suggested that during the acute phase of MI there is no additional measurable reduction in platelet survival above that observed in chronic coronary artery disease.

Thrombocytosis and platelet aggregates in the circulation of adjuvant arthritic rats

A marked increase in platelet count was observed in adjuvant-induced polyarthritic rats. Elevation of platelet count was still significant 3 months after onset of disease. Increased number and larger size of platelets reflect an increase in the rate of platelet production. By means of the platelet-count ratio technique, circulating platelet aggregates were demonstrated in rats with severe arthritis. Aspirin treatment prevented thrombocytosis and formation of platelet aggregates.

Platelet production in hypoxic and RBC-transfused mice.

Platelet production rates were studied in hypoxic, red blood cell (RBC) transfused, and normal mice. In addition, platelet depletion was induced in some of the mice by injection of rabbit anti-mouse platelet serum (RAMPS) to stimulate platelet production. Hypoxia alone caused an increase in haematocrit and platelet count at 1-3 d, followed by a decrease in platelet counts to below normal values at 6-7 d. On the otherhand, RBC transfusion caused increase haematocrit and decreased platelet count of mice at 1-4 d, with a return of platelet counts to normal by 5-6 d. Normal mice and mice transfused with RBC responded to platelet depletion with rebound-thrombocytosis with maximum platelet production 3-5 d later and elevated platelet counts on days 5-6. However, platelet production in platelet-depleted mice exposed to hypoxia was less marked, and platelet counts did not reach normal levels. The data are consistent with the hypothesis that hypoxia causes thrombocytopenia by stem cell competition between erythroid and megakaryocytic cell lines and/or inhibition of thrombopoietin production.

Stimulation of megakaryocytopoiesis by acute thrombocytopenia in rats

Rats were made acutely thrombocytopenic by injection of antiplatelet serum. Marrow sections and squash preparations were made at intervals during 120 hr. Determinations were made of mitotic index, stage of maturation, ploidy level, and cell size of megakaryocytes; number and size of platelets were measured. Increased endomitosis among megakaryocytes was followed by an increase in the proportion of immature megakaryocytes, a greater average ploidy level of recognized megakaryocytes, and larger megakaryocytes. Maximum changes in these several parameters occurred between 32 and 72 hr after induction of thrombocytopenia. By 120 hr all megakarocyte parameters were near normal. For about 3 days, beginning at about 36 hr, platelet numbers increased rapidly. Average platelet size rose and returned to normal within about 60 hr. Changes in ploidy and size of megakaryocytes were measured in the immature and mature maturation stages. The results suggest that the initial stimulus in response to acute thrombocytopenia acts primarily on diploid precursors, programming them to mature into a population of megakaryocytes with an average ploidy approximately one level greater than in normal rats and a proportionate increase in cell size. The larger megakaryocytes presumably produce more platelets, accounting for a major part of the increased rate of platelet production. Since the changes in megakaryocytes begin to reverse before circulating platelet numbers have reached the normal level, reversal of the stimulus appears to be initiated by some change other than platelet mass.

In vitro labelling of platelets: an experimental study on healthy asplenic subjects using two different incubation media.

Duplicate platelet survival studies, using autologous platelets labelled in vitro with radioactive sodium chromate, were performed on six young healthy asplenic men. In the first experiment plasma, and in the second a Ringer-citrate-dextrose (RCD) solution (Abrahamsen, 1968), was employed as incubation medium. The uptake of chromate by the platelets was about 2.5 times higher in the RCD compared to the plasma experiments. An identical pattern for the immediate behaviour of infused labelled platelets was observed in the duplicate studies, and the recovery of platelet-bound radioactivity remained stable at the 90% level during 2 h post-infusion. In these experiments the means for platelet mean life span (MLS) were identical, 7.2 +/- 0.5 and 7.2 +/- 0.4 days, respectively. These values slightly, but not significantly, exceeded the mean platelet MLS for a control group consisting of 10 young healthy males (6.9 +/- 0.4 days). The means for platelet production rate (P) at the duplicate studies made on the asplenic subjects were 19 +/- 2 X 10(10) and 21 +/- 2 X 10(10) platelets per day, respectively, and did not differ from the mean for P obtained in the control group (22 +/- 2 X 10(10).

The relation of thrombokinetics to bone marrow megakaryocytes in idiopathic thrombocytopenic purpura (ITP)

In 23 patients with untreated idiopathic thrombocytopenic purpura (TP), the relation of thrombokinetics to quantitative determinations of megakaryocytes in bone marrow sections was studied. The megakaryocytes were classified into maturation stages, and platelet sizes were determined. Megarkaryocyte number and volume per microliter of bone marrow were significantly higher in ITP as compared to controls. The megakaryocyte number and volume were inversely related to the peripheral platelet count. Platelet production rate was significantly increased in ITP and related to the megakaryocyte number and volume. The megakaryocytes were shifted towards more immature forms in ITP, suggesting an increased turnover rate of the expanded recognizable metakaryocyte compartment. Platelet size was significantly increased in ITP, and the mean platelet diameter was 1.6 times normal. There was a significant relationship between platelet size and platelet production rate, as well as an inverse relationship between platelet size and platelet mean life-span (MLS). There was also a significant correlation between platelet size and the proportion of young megakaryocytes.

The Relation of Thrombokinetics to Bone Marrow Megakaryocytes in Idiopathic Thrombocytopenic Purpura(ITP)

In 23 patients with untreated idiopathic thrombocytopenic purpura (TP), the relation of thrombokinetics to quantitative determinations of megakaryocytes in bone marrow sections was studied. The megakaryocytes were classified into maturation stages, and platelet sizes were determined. Megarkaryocyte number and volume per microliter of bone marrow were significantly higher in ITP as compared to controls. The megakaryocyte number and volume were inversely related to the peripheral platelet count. Platelet production rate was significantly increased in ITP and related to the megakaryocyte number and volume. The megakaryocytes were shifted towards more immature forms in ITP, suggesting an increased turnover rate of the expanded recognizable metakaryocyte compartment. Platelet size was significantly increased in ITP, and the mean platelet diameter was 1.6 times normal. There was a significant relationship between platelet size and platelet production rate, as well as an inverse relationship between platelet size and platelet mean life-span (MLS). There was also a significant correlation between platelet size and the proportion of young megakaryocytes.

Platelet producton and survival in cyanotic congenital heart disease.

Studies of platelet survival time, ‘turnover’, sequestration with use of 51Cr‐labelled platelets as well as platelet size distribution as an index of the age of platelet population and the rate of platelet production were performed in 13 patients with cyanotic congenital heart disease (CCHD). Platelet survival was significantly shorter in CCHD than in the normal subjects. The platelet population was younger in CCHD and the size distribution of platelets showed a shift to the right, i.e. the percentage proportion of megathrombocytes was increased (24–52 %) as compared with controls (6–15 %). The absolute number of megathrombocytes was also increased in some patients. The differences from the control values were statistically significant. The results suggested that an increased peripheral destruction of platelets (thrombocytolytic state) is present in children with CCHD.

Platelet Production in Experimental Iron Deficiency Anemia

Abstract Abnormal platelet counts have been observed in patients with iron deficiency anemia. To study this relationship, rats were made iron deficient, and platelet production was estimated by radiosulfate incorporation into platelets. With progressive iron deficiency anemia, both platelet counts and the rate of platelet production increased significantly. Platelet survival was normal. Injection of iron was followed by a fall in platelet counts and platelet production to normal levels within 72 hr, at which time stainable iron had appeared in the bone marrow. An inverse relationship between platelet counts and hematocrit was also seen. It appears that platelet homeostasis in iron deficiency anemia is influenced by the duration and severity of anemia.