Procoagulant, anticoagulant and fibrinolytic activities in llama plasma

Normal Hemostatic Profiles and Coagulation Factors in Healthy Free-Living Florida Manatees ( Trichechus manatus latirostris)

Hemostatic disorders presumptively play an important role in the pathophysiology of several important disease conditions in the Florida manatee ( Trichechus manatus latirostris). Prior to pursuing such clinical implications, it is essential to establish normal hemostatic profiles in clinically healthy animals. During annual health assessments of free-living manatees organized by the US Geological Survey, blood samples were collected from 12 healthy animals from the Atlantic coast and 28 from the Gulf of Mexico coast of Florida, with body lengths of 210-324 cm. The following analyses were performed on citrated plasma: prothrombin (PT), partial thromboplastin time (PTT), and concentrations of fibrinogen, D-dimers, and coagulation factors VII, VIII, IX, X, XI, and XII. Compared to other mammalian species, manatees had short PT (9.2±1.5 s) and PTT (10.7±0.5 s), fibrinogen was 369±78.7 mg/dL, antithrombin III was 132±11%, and D-dimer was 142±122 ng/mL. Baseline concentrations for the listed coagulation factors were established. When comparing coagulation factors between locations, Atlantic coast manatees had significantly higher factors VIII, IX, and X than did Gulf Coast manatees. This finding may reflect differences in water salinity, diet, or genetics. There were no differences in coagulation factors when among sexes and sizes. These baselines for hemostatic profiles and coagulation factors in healthy free-living manatees lay the foundation for diagnosis and future research of hemostatic disorders and contribute to understanding their role in the pathophysiology of manatees affected by various diseases.

Reference intervals for hematologic and coagulation tests in adult alpacas (Vicugna pacos)

BACKGROUND

Species-specific reference intervals are needed for interpretation of laboratory tests. Reference interval studies of alpacas have been limited by low numbers and use of outdated methods.

OBJECTIVES

The aims of this study were to establish reference intervals for hematologic and coagulation tests in alpacas using a laser-based hematology analyzer and a mechanical clot detection coagulation analyzer, respectively; to compare results for automated and manual differential WBC and platelet counts and fibrinogen concentrations; and to examine the effect of herd and sex on hematologic tests in a population of alpacas.

METHODS

Blood collected from clinically healthy female and male adult alpacas (Vicugna pacos) from 5 herds underwent full CBC analysis using an ADVIA 2120 (n = 65). Blood smears were examined for manual differential WBC counts, platelet estimates, and morphologic examination of blood cells. PCV and plasma protein and heat-precipitable fibrinogen concentration measured by refractometry were also determined. Partial thromboplastin time, prothrombin time, and clottable fibrinogen concentration were measured using a STA Compact analyzer (n = 13). Reference intervals were established using 2.5th and 97.5th percentiles for hematologic analytes and minimum and maximum values for coagulation tests. Automated and manual differential WBC counts, platelet counts, and fibrinogen concentrations were compared. Results were also evaluated for herd- and sex-associated effects.

RESULTS

Hematologic reference intervals for alpacas were similar to those reported previously, except for lower RBC-related results, which showed a herd bias. Correlations between automated and manual neutrophil, lymphocyte, eosinophil, and platelet counts were moderate to good, with weak to poor correlations for monocyte and basophil counts and fibrinogen concentrations. Owing to the low number of samples analyzed, reference intervals for coagulation tests should be considered estimated intervals.

CONCLUSIONS

Reference intervals will be useful guides for interpreting hematologic and coagulation results in alpacas, particularly when using the same instrumentation and reagents.

Comparative aspects of blood coagulation

Blood coagulation is a basic physiological defense mechanism that occurs in all vertebrates to prevent blood loss following vascular injury. In all species the basic mechanism of clot formation is similar; when endothelium is damaged a complex sequence of enzymatic reactions occurs that is localized to the site of trauma and involves both activated cells and plasma proteins. The reaction sequence is initiated by the expression of tissue factor on the surface of activated cells and results in the generation of thrombin, the most important enzyme in blood clot formation. Thrombin converts soluble fibrinogen, via soluble fibrin monomers, into the insoluble fibrin that forms the matrix of a blood clot as well as exerting positive-feedback regulation that effectively promotes additional thrombin generation that facilitates the rapid development of a thrombus. Both spontaneous and trauma-induced haemorrhagic episodes can develop in all mammals with inherited or acquired abnormalities in one or more of the coagulant proteins. Experimental studies with plasma from a wide range of species have led to the conclusion that there are extensive differences in the rates of thrombin generation and fibrin formation among species. However, current evidence suggests that at least some of these quantitative differences are likely due to the use of non-species specific laboratory reagents. Although the individual proteins involved in the procoagulant pathways exhibit similar functions in all animals, differences in amino acid sequence cause incomplete homology and varying degrees of immunological cross-reactivity for the same protein across species.