Coulter Counter studies of hypotonic-induced macrothrombocytosis in normal subjects and in idiopathic thrombocytopenic purpura patients

Human platelet osmotic water and nonelectrolyte transport

The osmotic water (Pf) and nonelectrolyte permeability (Ps) properties of human platelets were characterized using the stopped-flow light-scattering technique. At 37 degrees C, Pf = 0.007 +/- 0.001 cm/s, the urea reflection coefficient (sigma urea) = 0.95 +/- 0.04, and Ps for a series of permeant nonelectrolytes was (in cm X s-1 X 10(-6)) 2.1 (urea), 3.5 (glycerol), 3.8 (thiourea), 17 (ethylene glycol), 18 (acetamide), 23 (formamide), and 24 (butyramide). Pf did not depend on the size of the osmotic gradient or on the direction of volume flow. Mercurial sulfhydryl reagents did not inhibit osmotic water transport, and phloretin and phenylurea did not inhibit urea transport. There was a discontinuity in the temperature dependence for both Pf and urea permeability (P urea) at 36 degrees C; enthalpy (delta H) = 25 (greater than 36 degrees C) and 4.4 kcal/mol (less than 36 degrees C) for Pf, and delta H = 26 (greater than 36 degrees C) and 7 kcal/mol (less than 36 degrees C) for P urea. In contrast to the facilitated water and urea transport systems in the red blood cell, these results suggest that the mechanism for water and urea transport in the platelet is primarily by diffusion through membrane phospholipid. A computer-simulated model of platelet circulation through the renal medulla, based on the measured values for Pf, P urea, and sigma urea, indicated that platelets undergo an approximately 40% decrease in volume in the inner medulla and an approximately 20% overshoot in volume as they return to the external isosmotic environment.

Feline leukemia virus-induced thrombocytopenia and macrothrombocytosis in cats

The Kawakami-Theilen strain of feline leukemia virus (FeLV-KT), an exogenous anemia-inducing retrovirus, induced significant macrothrombocytosis and thrombocytopenia during acute infections of cats. The geometric mean platelet volumes of both freshly isolated fixed platelets and ethylenediamine tetraacetic acid-sphered platelets from infected cats were increased, but the ratio of fresh-fixed to ethylenediamine tetraacetic acid-sphered platelet volumes, an estimate of ethylenediamine tetraacetic acid-induced isovolumetric shape change, was normal. Total plasma membrane increased as the platelet volumes increased in FeLV-KT-infected cats, but estimated surface connected canalicular system surface area did not. Platelet concentrations were decreased 2 to 6 weeks after inoculation, but marked macrothrombocytosis resulted in a trend toward increased platelet mass on weeks 5 and 6 after inoculation. Thus, FeLV-KT-induced macrothrombocytosis may serve as a model of impaired platelet volume regulation. The platelet volume and platelet membrane surface area abnormalities found suggest that this model would allow studies of the megakaryocyte/platelet axis, particularly in the area of membrane formation and territorial demarcation.

Changes of platelet cell volumes in hypotonic solution

Changes of platelet cell volumes in hypotonic solution were studied by the use of a new apparatus for cell volume analysis. Continuous mean cell volume analyzer (CMA) is a computerized instrument which continuously counts the mean cell volume and records the results. Moreover, it also shows patterns of expansion or shrinkage. Adequate amounts of platelet rich plasma were added into 0.8 or 0.4% of NaCl solution containing 5mM phosphate buffer. The mean platelet volumes were measured continuously every 2 seconds for 200 seconds. In isotonic solution, platelets changed their volumes little, but in hypotonic solution, the volumes increased for about 20 seconds and then, decreased gradually. Platelet volume expansion ratio and shrinkage ratio were calculated from these patterns. The shrinkage ratio well corresponded to the values of hypotonic shock response measured by spectrophotometry (r = 0.861). Expansion and especially shrinkage ratios decreased during storage, and they were dependent on stored temperature and pH.

Sex-related differences in platelet morphology in whole blood (WB) and platelet-rich plasma (PRP)

The proportion of smooth, disc-shaped platelets (D) in freshly drawn, glutaraldehyde fixed whole blood (WB) and citrated platelet-rich plasma prepared at 37 degrees C is compared for male (N = 55) and female (N = 31) donors. Female donors have significantly more %D than male donors and the variability in %D measured on repeated occasions over a period of 3-69 months is less for female donors. WB and PRP gave similar results. The sex-related differences in %D were not related to hematocrit or to concomitant use of oral contraceptives. There were no significant sex-related differences in platelet mean volume or in platelet plasma membrane surface area as determined by the osmotic spherocyte method. However, the volume of D is smaller for male donors. It is concluded that the sex-related differences in platelet morphology do not represent intrinsic differences in platelet size or measurable total plasma membrane but represent a selective shape change activation of the larger D in the circulation of male donors. The significance of these observations for the sex-related differences in risk of cardiovascular disease and efficacy of anti-thrombotic therapy awaits appropriate prospective epidemiological studies.

A stable human platelet-white blood cell control for the Coulter Model S-Plus II

The preparation and evaluation of a human platelet-white blood cell control of at least 5 months' stability, as measured in the Coulter Counter Model S-Plus II, is described. In some preparations minor departures from log normal platelet (PLT) distributions were found, impeding the generation of values for mean PLT volume (MPV) and PLT distribution width (PDW). In many cases, however, excellent linearity for PLT and white blood cell (WBC) counts and low coefficients of variation for PLT and WBC counts and PDW were found. Some possible factors causing the large coefficient of variation found for MPV values are mentioned.