Storage Pool Deficiency Research Articles

Heterogeneous defects of platelet secretion and responses to weak agonists in patients with bleeding disorders.

Eleven patients with mild bleeding disorders had as a common abnormality, impaired platelet aggregation and secretion with low concentrations (0.5-1.0 micrograms/ml) of collagen and, in most cases, an absence of second phase aggregation with epinephrine. Platelet granule contents were normal, ruling out storage pool deficiency. To characterize further the platelet abnormalities, we measured aggregation, 14C-5HT secretion, and TxB2 formation induced by a variety of platelet agonists. In eight of the 11 patients we observed decreased initial rates as well as extents of aggregation with one or more weak agonists (ADP, epinephrine, thromboxane A2 and the endoperoxide analogue U44069), i.e. agonists which induced secretion only as a result of aggregation, but normal responses to strong agonists such as arachidonate and high (10 micrograms/ml) concentrations of collagen, which can induce secretion in the presence or absence of aggregation. In all of these patients, TxB2 formation with arachidonate and all concentrations of collagen was normal. The platelet defects in these eight patients have been designated as weak agonist response defects (WARDs). In contrast, the initial aggregation responses to all weak agonists were normal in the three other patients, while secretion and TxB2 formation induced by strong agonists were impaired. Thus, in contrast to the eight patients above, the platelet defects in these three patients were characteristic of defects in the secretion response per se. The results obtained in the 11 patients studied indicate that these types of platelet disorders, previously referred to as primary secretion defects, include defects in the initial platelet responses which precede secretion (WARD) as well as defects in the secretory mechanism per se. Both groups of defects appear to be heterogeneous in nature.

1-Desamino-8-D-arginine vasopressin (desmopressin) shortens the bleeding time in storage pool deficiency.

Excerpt Patients with congenital or acquired storage pool deficiency have a mild to moderately severe bleeding tendency, characterized by epistaxis; menorrhagia; easy bruising; and prolonged bleedi...

ADP Plays a Key Role in Thrombogenesis in Rats

The relative importance of ADP, arachidonic acid metabolites and serotonin as thrombogenic factors was evaluated in rats by comparing, after oral administration, the effects of two inhibitors of ADP-induced platelet aggregation (ticlopidine and PCR 4099), three cyclo-oxygenase inhibitors (aspirin, triflusal and indobufen) and a selective serotonin 5HT2 receptor antagonist (ketanserin) on platelet aggregation, in four platelet-dependent thrombosis models and on bleeding time. Platelet aggregation induced by ADP and collagen was completely inhibited by ticlopidine and PCR 4099 whereas only the collagen aggregation was reduced by the cyclo-oxygenase inhibitors. Ketanserin or a depletion of platelet serotonin by reserpine did not affect platelet aggregation. Ticlopidine and PCR 4099 greatly prolonged rat tail transection bleeding time. This is probably related to their known ability to inhibit ADP-mediated platelet aggregation. In contrast, the cyclooxygenase inhibitors did not affect bleeding time at all. Reserpine and ketanserin prolonged bleeding time by interfering with the action of serotonin on the vascular wall. Ticlopidine and PCR 4099 were very potent antithrombotics in all the models. Aspirin, only at a high dose, inhibited poorly thrombus formation on a silk thread in an arterio-venous shunt, suggesting that the inhibition of cyclo-oxygenase was not responsible. Triflusal was inactive in all models while indobufen slightly reduced thrombus formation in the silk thread and metallic coil models. Ketanserin and reserpine reduced thrombus only in the metallic coil model. Thrombus formation was greatly reduced in fawn-hooded rats, which lack ADP in their platelet dense granules because of a genetic storage pool deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary artery pressure in rats with hereditary platelet function defect.

Pulmonary vasoactivity of several biochemical components produced or stored in platelet was the justification for the study of pulmonary artery pressure in fawn-hooded rats (FHR) with hereditary platelet storage pool deficiency. Anesthetized (pentobarbital 35 mg kg-1 i.p.) FHR had higher right ventricular systolic pressure compared with normal Wistar rats (NWR) matched in sex and age (57.7 +/- 6.8 vs. 34.8 +/- 1.2 mm Hg; p less than 0.01). The incidence of higher pulmonary artery pressure (greater than means + 2 SD of NWR) was 68% among FHR. A significant difference was recorded between FHR and NWR in the relative weight of the right ventricle (0.092 +/- 0.021 vs. 0.048 +/- 0.001 g/100 g; p less than 0.05). Rise in pulmonary artery pressure in FHR after 4 weeks of normobaric hypoxia was found to be comparable to that seen posthypoxically in NWR. Morphological consequences of pulmonary hypertension, ranging from moderate medial hypertrophy of small arteries to muscularization of pulmonary arterioles, were recorded in about 50% of FHR with increased pulmonary artery pressure.

Platelet volume and intraplatelet adenine nucleotides in various hematologic disorders.

By recent advanced techniques, blood platelets have proved to be varied in size and metabolism in various hematologic disorders. We examined platelet volume and intraplatelet adenine nucleotides in 36 patients with various hematologic disorders in order to clarify the quantitative platelet abnormalities. Platelet volumes were smaller in patients with acute leukemia and aplastic anemia, and larger in patients with immune thrombocytopenic purpura (ITP). The amount of intraplatelet ADP was decreased and ATP/ADP ratio was increased in acute leukemia, aplastic anemia and myeloproliferative disorders (MPD), which strongly suggested the presence of storage pool deficiency in these patients. Intraplatelet ADP per volume was decreased in acute leukemia, aplastic anemia and MPD, and ATP per volume was decreased in aplastic anemia. ATP content was increased in ITP in proportion to the increased platelet volume. These parameters were examined in 36 patients with the following hematologic disorders: 7 acute leukemia treated with cytotoxic chemotherapy, 5 aplastic anemia, 3 paroxysmal nocturnal hemoglobinuria (PNH), 9 immune thrombocytopenic purpura (ITP), 5 hypersplenism and 7 myeloproliferative disorders (MPD).

Patients with a prolonged bleeding time and normal aggregation tests may have storage pool deficiency: studies on one hundred six patients

One hundred six patients with storage pool deficiency (SPD) were studied with respect to platelet count, bleeding time, total platelet ATP and ADP, platelet serotonin, and in vitro aggregation. The diagnosis of SPD was made on basis of a prolonged bleeding time, a decreased total platelet ADP, and a diminished level of serotonin. Fifty-one patients from 34 unrelated families had congenital SPD, and 55 patients had acquired SPD. Congenital SPD was a common disorder in patients with a lifelong bleeding tendency and a prolonged bleeding time. The frequency in this group of patients was 18%, about one-half the frequency of von Willebrand's disease (vWd). Twenty-three percent of all patients had normal aggregation responses to ADP, epinephrine, and collagen; 33% had aggregation tracings typical for a secretion defect; and 44% had miscellaneous aggregation abnormalities. These findings indicate that SPD is common, heterogeneous, and not necessarily associated with in vitro aggregation abnormalities.

Patients With a Prolonged Bleeding Time and Normal Aggregation Tests May Have Storage Pool Deficiency: Studies on One Hundred Six Patients

One hundred six patients with storage pool deficiency (SPD) were studied with respect to platelet count, bleeding time, total platelet ATP and ADP, platelet serotonin, and in vitro aggregation. The diagnosis of SPD was made on basis of a prolonged bleeding time, a decreased total platelet ADP, and a diminished level of serotonin. Fifty-one patients from 34 unrelated families had congenital SPD, and 55 patients had acquired SPD. Congenital SPD was a common disorder in patients with a lifelong bleeding tendency and a prolonged bleeding time. The frequency in this group of patients was 18%, about one-half the frequency of von Willebrand's disease (vWd). Twenty-three percent of all patients had normal aggregation responses to ADP, epinephrine, and collagen; 33% had aggregation tracings typical for a secretion defect; and 44% had miscellaneous aggregation abnormalities. These findings indicate that SPD is common, heterogeneous, and not necessarily associated with in vitro aggregation abnormalities.

The influence of lysophosphatidic acid on platelet protein phosphorylation.

Lysophosphatidic acid (LPA) is a lysophospholipid that is produced during thrombin stimulation of platelets, which can promote platelet aggregation. The mechanism of the effect of LPA was explored in normal platelets and in platelets from a patient with a storage pool deficiency (SPD). A comparison with other lysophospholipids showed that only LPA exerted significant effects to cause or potentiate platelet aggregation. Aspirin, an inhibitor of prostaglandin endoperoxide synthetase, had little effect on LPA-induced aggregation, but completely blocked LPA-induced serotonin secretion. LPA also promoted phosphorylation of myosin light chain (MLC), a 47 kilodalton (kDa) protein, and actin-binding protein. Aspirin significantly inhibited the phosphorylation of the 47-kDa and actin-binding proteins at 3-8 min after the addition of LPA, but had no effect on protein phosphorylation within the 1st min and had no significant effect on MLC phosphorylation. In SPD platelets, aspirin partially inhibited both aggregation and phosphorylation of the 47-kDa protein (less than 30% inhibition) and MLC (less than 40% inhibition) at time points of 1 min or less. The addition of ADP to SPD platelets enhanced the LPA response in platelets either pretreated or not pretreated with aspirin. Studies with SPD platelets indicate that thromboxane and secreted ADP contribute to, but are not necessary for, LPA-induced aggregation and phosphorylation. A23187 (a calcium ionophore) and LPA showed some selectivity to promote MLC as opposed to the 47-kDa protein phosphorylation, particularly at low concentrations of agonists and at earlier time points. The protein phosphorylation changes seen are consistent with a role for MLC phosphorylation in the granule centralization promoted with LPA.

The 5-hydroxytryptamine system of blood platelets: physiology and pathophysiology

The 5-hydroxytryptamine (5HT)-system of human blood platelets consists of a relatively specific uptake mechanism for 5HT at the plasma membrane, intracellular storage organelles (dense bodies), a metabolizing enzyme (monoaminoxidase B) and a 5HT 2-receptor whose stimulation leads to activation of the phosphatidylinositide turnover, a rise in free cytoplasmic Ca 2+, phosphorylation of proteins and a shape change reaction. There is neither a relevant 5HT-biosynthesis nor a marked physiological 5HT-turnover in platelets. Under physiological conditions the platelet 5HT-system may have a role as a scavenger for free extracellular 5HT and in hemostasis. Disturbances which have been described in pathophysiological states include impairment of 5HT-uptake (hypertension, migraine), impairment of 5HT-storage (storage pool deficiencies, thromboembolic disorders, hypertension) and increased sensitivity to activating agents like 5HT (cardiovascular disorders, diabetes). Besides their role in physiology and pathophysiology platelets may be useful partial models for vascular smooth muscle cells.

Chediak-Higashi syndrome.

The use of cytochemical, electron microscopic, immunofluorescent, and tissue culture techniques has led to important advances in our understanding of the mechanisms underlying the pathogenesis of the Chediak-Higashi syndrome (CHS). This rare and fatal autosomal recessive disorder is clinically characterized by partial albinism, frequent pyogenic infections, and an accelerated lymphohistiocytic phase. The pathological hallmark of CHS is the presence in all white blood cells of massive lysosomal inclusions, which are formed through a combined process of fusion, cytoplasmic injury, and phagocytosis. The abnormal inclusions exhibit both azurophilic and specific granular markers, and are probably responsible for most of the impaired leukocyte and other cell functions in CHS patients. In addition, a selective profound natural killer (NK) cell function and platelet storage pool deficiencies have been described in these patients. Impaired microtubule assembly and functions, mediated by abnormal intracellular cyclic nucleotide levels, which could be corrected by treatment with ascorbic acid, were suggested to be the pathophysiological basis for CHS abnormalities. However, some recent studies have questioned this cytoskeletal model, which is suggested to be rather a secondary manifestation of CHS.

Changes in platelet β‐thromboglobulin, fibrinogen, albumin, 5‐hydroxytryptamine, ATP, and ADP during and after surgery with extracorporeal circulation in man

Surgery with extracorporeal circulation (ECC) is associated with transient alterations of platelet function whose pathogenic mechanisms are not completely understood. To define further the platelet abnormalities, we determined the changes in platelet content of several granule-associated substances during and after ECC in patients subjected to aortocoronary bypass surgery. Platelet beta-thromboglobulin (beta-TG) decreased to 79.8% of the preoperative level at the end of ECC (p less than 0.01) and, as expected, did not recover 1 hr after the end of surgery. Platelet fibrinogen and albumin decreased to 67.9% (p less than 0.01) and to 29.8% (p less than 0.01) of baseline, respectively. However, 1 hr after surgery, platelet fibrinogen rose to 92% and albumin to 55.5% of baseline, denoting that during the recovery from ECC, platelets incorporate some plasma proteins. During ECC, platelet 5-hydroxytryptamine (5-HT) and total ATP and ADP decreased to 50.8% (p less than 0.01), 63.2% (p less than 0.01), and 69.9% (p less than 0.01) of their respective preoperative values, indicating dense body release. One hour after surgery, ATP recovered to 83.8%, suggesting that previous depletion compromised also the metabolic pool of adenine nucleotides. In summary, Our results confirm and extend previous observations demonstrating alpha-granule release during ECC. Platelets undergoing ECC can incorporate plasma proteins as evidenced by the rapid increase of platelet fibrinogen and albumin after bypass. Although the mechanisms of this increase and site of storage of the exogenous substances are unknown, this observation justifies further studies to determine if internalization of plasma proteins, especially fibrinogen, may take place in physiological conditions. Dense body depletion with transient storage pool deficiency appears to be a component of the reduced platelet function during ECC. Consumption of metabolic ATP with alteration of platelet energy metabolism may further impair platelet function, contributing to the bleeding episodes observed during surgery with ECC.

Platelet storage pool deficiency in pigs

We report a new bleeding disease--storage pool deficiency (SPD) of platelets--in pigs from the Mayo swine colony of homozygous von Willebrand's disease (vWD) and of heterozygous carriers of vWD. Levels of factor VIII, von Willebrand factor antigen (vWF:Ag), and ristocetin cofactor (RCof) were similar in the vWD carriers and SPD pigs. The latter pigs, however, had bleeding times of 15 minutes or more and were severe bleeders, in contrast to clinically normal vWD carriers. Platelet aggregation in response to collagen was reduced in most SPD pigs. Total platelet content of ADP, ATP, and serotonin was less than that of normal pigs. While the initial uptake of 14C-labeled serotonin into platelets was similar in SPD and normal pigs, retention of serotonin was reduced in platelets of SPD pigs. Transmission electron microscopy showed a large decrease of dense bodies in the platelets of SPD pigs. These findings support a diagnosis of SPD. Genetic analyses suggest an autosomal recessive mode of inheritance. A breeding program is under way to produce pigs affected only at the SPD gene, thus allowing further characterization of SPD and SPD-carrier pigs.

Platelet Storage Pool Deficiency in Pigs

We report a new bleeding disease--storage pool deficiency (SPD) of platelets--in pigs from the Mayo swine colony of homozygous von Willebrand's disease (vWD) and of heterozygous carriers of vWD. Levels of factor VIII, von Willebrand factor antigen (vWF:Ag), and ristocetin cofactor (RCof) were similar in the vWD carriers and SPD pigs. The latter pigs, however, had bleeding times of 15 minutes or more and were severe bleeders, in contrast to clinically normal vWD carriers. Platelet aggregation in response to collagen was reduced in most SPD pigs. Total platelet content of ADP, ATP, and serotonin was less than that of normal pigs. While the initial uptake of 14C-labeled serotonin into platelets was similar in SPD and normal pigs, retention of serotonin was reduced in platelets of SPD pigs. Transmission electron microscopy showed a large decrease of dense bodies in the platelets of SPD pigs. These findings support a diagnosis of SPD. Genetic analyses suggest an autosomal recessive mode of inheritance. A breeding program is under way to produce pigs affected only at the SPD gene, thus allowing further characterization of SPD and SPD-carrier pigs.

Controlled trial of desmopressin in liver cirrhosis and other conditions associated with a prolonged bleeding time

The synthetic vasopressin derivative desmopressin (DDAVP) shortens a prolonged bleeding time (BT) in patients with uremia, congenital platelet dysfunction, and von Willebrand disease. To establish the limits of the clinical usefulness of DDAVP, a controlled randomized study was carried out in 53 patients and ten volunteers with different conditions that have in common a prolonged BT. DDAVP significantly shortened the BT in 21 cirrhotics (P less than .01), in eight patients with unclassified prolonged BT (P less than .05) and in ten volunteers taking the antiplatelet drugs aspirin (P less than .05) and ticlopidine. The BT changes were not statistically significant in 15 patients with severe thrombocytopenia nor in nine with congenital platelet dysfunction, even though a few patients with storage pool deficiency responded with a marked BT shortening. Our findings indicate that DDAVP might be given when biopsies or other surgical procedures must be carried out in patients with prolonged BT. However, the compound is often ineffective in patients with thrombocytopenia or congenital platelet dysfunction.

Controlled Trial of Desmopressin in Liver Cirrhosis and Other Conditions Associated With a Prolonged Bleeding Time

The synthetic vasopressin derivative desmopressin (DDAVP) shortens a prolonged bleeding time (BT) in patients with uremia, congenital platelet dysfunction, and von Willebrand disease. To establish the limits of the clinical usefulness of DDAVP, a controlled randomized study was carried out in 53 patients and ten volunteers with different conditions that have in common a prolonged BT. DDAVP significantly shortened the BT in 21 cirrhotics (P less than .01), in eight patients with unclassified prolonged BT (P less than .05) and in ten volunteers taking the antiplatelet drugs aspirin (P less than .05) and ticlopidine. The BT changes were not statistically significant in 15 patients with severe thrombocytopenia nor in nine with congenital platelet dysfunction, even though a few patients with storage pool deficiency responded with a marked BT shortening. Our findings indicate that DDAVP might be given when biopsies or other surgical procedures must be carried out in patients with prolonged BT. However, the compound is often ineffective in patients with thrombocytopenia or congenital platelet dysfunction.

Diagnosis of storage pooldeficiency by determination of diadenosine 5′, 5‴-P 1 ,P 4 -tetraphosphate in whole blood

Platelets from cat and cattle with Chediak-Higashi disease were found completely devoid of AP 4 A as measured by high performance liquid chromatoraphy. Using a very sensitive firefly biolumnescence method 6% of the normal content of AP 4A was, however, found in platelets from sick animals. A content of Ap A of 1.90 ± 0.11 × 10 M (means ± SEM, n = 10) was found in whole normal human blood as measured by firefly bioluminescense method in trichloroacetic acid extracts of the blood samples. This concentration corresponds to the contribution from the platelets, thus the contribution of Ap 4A from erythrocytes and the “buffy-coat” is negligible. Using the same method an AP 4A contents in platelets of 0.063 and 0.021 nmol/mg of protein compared to the normal content of 0.42 nmol/mg of protein (1) was found in two patients with severe myeloproliferative disorder calculated in this way on basis of platelet counts and on the assumption that 10 11 platelets contain 189 mg of protein (2). Comparison of these figures with parallel HPLC analyses on acid extracts of platelets isolated from the same patient were in agreement. The storage pool deficiency of adenine nucleotides in this disease found by others on basis of release experiments (3) can thus be diagnosed by rapid and simple measurements of Ap 4A in whole blood using the advantage of Ap 4A being a specific components stored in dense granules.

Platelet Adhesion and Thrombus Formation on Subendothelium in Platelets Deficient in Glycoproteins IIb-IIIa, Ib, and Storage Granules

Abstract Patients whose platelets are deficient in glycoprotein (GP) Ib, IIb- IIIa (thrombasthenia), or granule substances (storage pool deficiency, SPD) were studied to define further the properties of platelets that mediate platelet adhesion and thrombus formation on subendothelium. Both nonanticoagulated and citrated blood were exposed to everted, de- endothelialized rabbit vessel segments under controlled flow conditions and shear rates varying from 650 to 3,300 sec-1. Morphometry was used to measure platelet thrombus dimensions and the percentage of the subendothelial surface covered with contact (C) or spread (S) platelets. Adhesion was defined as C + S. The results in SPD demonstrated (1) reduced thrombus dimensions in delta-SPD (pure dense granule deficiency) in proportion to the magnitude of the dense granule defect; (2) an even greater reduction in thrombus dimensions in patients with combined deficiencies of alpha and dense granules (alpha delta-SPD); and (3) impaired platelet adhesion at several conditions in alpha delta-SPD and, in delta-SPD, a hematocrit-dependent impairment of adhesion in citrated blood at 2,600 sec-1. In thrombasthenia, platelets were present as a monolayer on the subendothelial surface in both nonanticoagulated and citrated blood, indicating an absolute requirement for GPIIb-IIIa in promoting platelet-platelet interaction at all shear rates and perfusion times. Two types of abnormalities in platelet-vessel wall interactions were observed. In nonanticoagulated blood, the percentage of platelets in the C phase was consistently increased at all shear rates, but C + S values were normal. These observations indicate that platelets deficient in GPIIb-IIIa do not spread normally on the subendothelial surface exposed to nonanticoagulated blood. With citrated blood, the C + S value in thrombasthenia was reduced at both 800 and 2,600 sec-1, as in von Willebrand's disease, and a similar degree of reduction (about 50%) was observed in normal blood treated with a monoclonal antibody to GPIIb- IIIa. The findings, together with theoretical considerations, are consistent with an hypothesis that GPIIb-IIIa mediates the spreading of platelets on subendothelium following the initial attachment through GPIb and that GPIIb-IIIa may be considered an adhesion site on the platelet membrane. Abnormalities of GPIIb-IIIa may, depending on the conditions of study, result in either increased values of C platelets or decreased values of C + S. The results of the study further suggest that a complex interaction of platelet granule factors and membrane GP mediate platelet adhesion and thrombus formation.

Platelet adhesion and thrombus formation on subendothelium in platelets deficient in glycoproteins IIb-IIIa, Ib, and storage granules

Patients whose platelets are deficient in glycoprotein (GP) Ib, IIb-IIIa (thrombasthenia), or granule substances (storage pool deficiency, SPD) were studied to define further the properties of platelets that mediate platelet adhesion and thrombus formation on subendothelium. Both nonanticoagulated and citrated blood were exposed to everted, de-endothelialized rabbit vessel segments under controlled flow conditions and shear rates varying from 650 to 3,300 sec-1. Morphometry was used to measure platelet thrombus dimensions and the percentage of the subendothelial surface covered with contact (C) or spread (S) platelets. Adhesion was defined as C + S. The results in SPD demonstrated (1) reduced thrombus dimensions in delta-SPD (pure dense granule deficiency) in proportion to the magnitude of the dense granule defect; (2) an even greater reduction in thrombus dimensions in patients with combined deficiencies of alpha and dense granules (alpha delta-SPD); and (3) impaired platelet adhesion at several conditions in alpha delta-SPD and, in delta-SPD, a hematocrit-dependent impairment of adhesion in citrated blood at 2,600 sec-1. In thrombasthenia, platelets were present as a monolayer on the subendothelial surface in both nonanticoagulated and citrated blood, indicating an absolute requirement for GPIIb-IIIa in promoting platelet-platelet interaction at all shear rates and perfusion times. Two types of abnormalities in platelet-vessel wall interactions were observed. In nonanticoagulated blood, the percentage of platelets in the C phase was consistently increased at all shear rates, but C + S values were normal. These observations indicate that platelets deficient in GPIIb-IIIa do not spread normally on the subendothelial surface exposed to nonanticoagulated blood. With citrated blood, the C + S value in thrombasthenia was reduced at both 800 and 2,600 sec-1, as in von Willebrand's disease, and a similar degree of reduction (about 50%) was observed in normal blood treated with a monoclonal antibody to GPIIb-IIIa. The findings, together with theoretical considerations, are consistent with an hypothesis that GPIIb-IIIa mediates the spreading of platelets on subendothelium following the initial attachment through GPIb and that GPIIb-IIIa may be considered an adhesion site on the platelet membrane. Abnormalities of GPIIb-IIIa may, depending on the conditions of study, result in either increased values of C platelets or decreased values of C + S. The results of the study further suggest that a complex interaction of platelet granule factors and membrane GP mediate platelet adhesion and thrombus formation.

Platelet granule disorders

The present review has cataloged the inherited and acquired disorders of platelet granules. Unfortunately, a mere listing of different conditions in which dense bodies, alpha granules, or both are decreased, absent, or fused does little to define their importance in human platelet physiology or as a causative factor in hemorrhagic disease. The inherited disorders serve as the best index of granule involvement in platelet hemostatic function. Our experience with storage pool deficiency in patients with Hermansky-Pudlak syndrome has suggested that in many individuals virtual absence of dense bodies and their contents does not present a serious threat to hemostasis. Placing HPS patients on aspirin did not cause spontaneous hemorrhage, suggesting that secretion of dense body contents and synthesis of endoperoxides and thromboxane A2 are not absolutely essential for platelet function. However, the literature strongly suggests that many patients with HPS and SPD face a serious risk from bleeding, and hemorrhage may cause death. We can only conclude that some patients with HPS have platelet defects or other hemostatic problems that render SPD a far more serious threat than in other patients who appear to have the same disease. Dense bodies of and by themselves do not appear absolutely required for platelet function. Isolated deficiency of alpha granules presents the same enigma. Only a few patients with this rare inherited disease have been reported. They are generally considered to have mild to severe hemorrhagic problems. However, the past medical history of our two patients with GPS has recently been reviewed and platelet function studies repeated. Despite the mild thrombocytopenia, they are free of any significant bleeding episodes and their platelet function appears virtually normal. Our findings do not support the concept that alpha granules are essential for platelet function. The only condition that seems to support a critical role for storage organelles in hemostasis is the combined alpha-granule, dense body deficiency in one patient reported by Weiss. This patient does have bleeding problems. However, it is difficult to draw conclusions based on a single patient, and the discovery of other patients will help to clarify the hemostatic problem of patients with dual storage organelle deficiencies. In the meantime, we have prepared platelets from normal individuals free of storage granules by sedimentation through gradients containing cytochalasin B. The function of the normal agranular platelets is compromised, but they do respond to some aggregating agents.(ABSTRACT TRUNCATED AT 400 WORDS)

Correction of symptoms of platelet storage pool deficiency in animal models for Chediak-Higashi syndrome and Hermansky-Pudlak syndrome

Two human diseases of platelet storage pool deficiency (SPD), Hermansky- Pudlak syndrome and Chediak-Higashi syndrome, are recessively inherited disorders characterized by hypopigmentation, prolonged bleeding, and normal platelet counts accompanied by a reduction in dense granule number. We have recently described seven independent recessive mutations in the mouse regulated by separate genes which are likely animal models for human SPD. Reciprocal bone marrow transplants were carried out between normal C57BL/6J mice and two of these mutants, beige and pallid, in order to test whether the platelet defects are due to a defect in platelet progenitor cells or to humoral factors. Normal and congenic mutant mice were transplanted with marrow after 950 rad whole body radiation. The long bleeding times and low serotonin concentrations of the two mutants were converted to normal values after transplantation with normal marrow. Likewise, normal mice displayed symptoms of SPD when transplanted with mutant marrow. These studies demonstrate that with each of the two mutations, platelet SPD results from a defect in bone marrow precursor cells. Also, the studies suggest that in severe cases, platelet SPD may be successfully treated by bone marrow transplantation.