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© 2006 The American Society for Nutrition J. Nutr. 136:2055S-2057S, July 2006

Supplement: The WALTHAM International Sciences Symposia Innovations in Companion Animal Nutrition: Poster Presentations

Platelet Taurine Concentration Can Be Predicted from Whole Blood Taurine Concentrations in Dogs1,2

Cristina L. Torres*,3, Naomi J. Walker{dagger}, Quinton R. Rogers* and Fern Tablin{dagger}

* Department of Molecular Biosciences and {dagger} Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California, Davis, CA

3 To whom correspondence should be addressed. E-mail: crestorres{at}hotmail.com.

KEY WORDS: • taurine • dog • platelet function • whole blood taurine

Clot formation is a protective mechanism that animals have evolved to minimize blood loss when a vessel has been disrupted. The actual clotting formation is a complex signaling reaction in which a multitude of factors are involved. Blood taurine concentration has been suggested as a modulating factor in the clotting cascade. Upon taurine depletion in cats, platelet taurine concentration decreases, and as a result, the rate of ex vivo aggregation increases (1). In human blood, ex vivo taurine supplementation increases the resistance to platelet aggregation, the latter being correlated with decreased thromboxane release during aggregation. To the authors' knowledge, there are no studies that determine whether a similar enhancement of clot formation occurs in taurine deficient dogs. This study was designed to determine whether taurine depletion in dogs affects platelet taurine concentration and function.


   MATERIALS AND METHODS
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 MATERIALS AND METHODS
RESULTS
 DISCUSSION
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The study protocols were approved by the Animal Use and Care Committee at the University of California, Davis and complied with the NRC guidelines for research animals (2). Thirteen male adult mixed-breed dogs were fed a 16% crude protein experimental lamb-meal and rice-bran diet (no taurine added) to maintain a constant body weight. The experimental group had 4 g of cholestyramine/d added to their diet to induce taurine depletion. The control group received no cholestyramine.

Fifteen milliliters of blood were collected from 6 taurine-sufficient dogs (Tau+) and 7 taurine-deficient dogs (Tau–). Dogs with blood taurine concentrations <180 nmol/mL were considered taurine deficient. Blood cell counts and platelet counts were performed using automated standard procedures. Taurine concentrations for whole blood and platelets were done using procedures previously described (3). Three dogs were excluded from analyses because of sample handling problems.

Platelets, platelet rich plasma (PRP) and platelet poor plasma (PPP) separations were done using a modification of the protocol by Field et al. (4). Sodium citrate was used as the anticoagulant agent. PRP and PPP were harvested after consecutive centrifugations at 312.5 x g for 20 min and 1800 x g for 10 min, respectively. Platelet pellets were resuspended with 6% dextran in sterile saline at 37°C. Ex vivo platelet function was measured by optical aggregometry (OA) and whole blood electric impedance aggregometry (WBEI) using collagen as a platelet agonist. Results were analyzed using Student's t test to estimate difference between groups (Systat 9, SPSS). P ≤ 0.05 was taken as an indication of statistical differences and a P > 0.05 < 0.10 was taken as a trend. Values reported in the text are means ± SEM.


   RESULTS
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 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 LITERATURE CITED
 
CBC counts did not differ between groups (Table 1). Blood taurine concentrations were 201 ± 18 (range from 168 to 268 nmol/mL) and 78 ± 12 nmol/mL in dogs (range from 44 to 108 nmol/mL) for Tau+ and Tau– groups, respectively (means ± SEM; P = 0.001), (Fig. 1). Platelet taurine concentrations were greater (P = 0.01) in Tau+ than in Tau– groups (442 ± 51 and 212 ± 64 nmol/106 platelets, respectively).


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  		TABLE 1 Complete blood count of taurine-sufficient (Tau +) and taurine-deficient (Tau –) male adult dogs1

 

Figure 1
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  		FIGURE 1  Whole blood and platelet taurine concentrations from taurine-sufficient (Tau+; n = 5) and taurine-deficient (Tau–; n = 5) male adult dogs. Values are means ± SEM. Analyses were performed using Student's t test. Differences between groups, *P < 0.05. Three dogs were excluded from analyses because of sample handling problems.

 
Blood taurine was better correlated to platelet taurine concentrations in the Tau+ group (r = 0.94) than in the Tau– group (r = 0.63). Overall, blood and platelet taurine concentrations were well correlated (r = 0.76) when the data were analyzed all together [Blood taurine (nmol/mL) = 0.367*platelet taurine (nmol/mL) + 19.1; R2 = 0.76] (Fig. 2). Ex vivo collagen-stimulated aggregation (OA) did not differ between groups, 63 ± 8 and 51 ± 12% for Tau+ and Tau–, respectively (P = 0.63). Lag time (WBEI) did not differ between groups (00:03:36 ± 00:02:28, Tau+ vs. 00:00:02 ± 00:00:001, Tau–; P = 0.16), nor the slope of 5.0 ± 0.7 vs. 4.0 ± 0.2, respectively; P = 0.20) (Table 2).


Figure 2
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  		FIGURE 2  Correlation of whole blood and platelet taurine concentrations in male adult dogs. {square} represents taurine-sufficient dogs (Tau+, n = 5); {blacksquare} represents taurine-deficient dogs (Tau–, n = 5). Three dogs were excluded from regression because of sample handling problems.

 

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  		TABLE 2 Ex vivo platelet response in taurine-sufficient (Tau+) and taurine-deficient (Tau–) dogs to 10 µL of collagen stimulus1

 

   DISCUSSION
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 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
LITERATURE CITED
 
An increasing number of reports of taurine deficient dogs have been published in the last 10 years. The determination of normal and deficient ranges of plasma and whole blood taurine concentrations is suggested to be different from that of cats. According to some authors, dogs with whole blood taurine concentrations below 180 nmol/mL are considered at risk for deficiency (5). In this study, platelet taurine concentrations from 5 taurine-deficient dogs were compared with platelet taurine concentration from 5 taurine-sufficient dogs. There is a direct correlation between plasma taurine concentrations and platelet taurine concentrations. Other studies report a direct correlation between plasma and platelet taurine concentrations in cats and in humans (6,7). Whole blood taurine concentrations, rather than plasma taurine concentrations, have fewer fluctuations in taurine status; therefore, whole blood was chosen to establish the correlation with platelet taurine concentration in this dog study.

Platelets from taurine-deficient cats and humans are more sensitive to clotting stimulus than their taurine-sufficient counterparts (1). In the present study, platelet function was measured by 2 different assays. We found that the proportion of aggregation and speed of aggregation between Tau+ and Tau– groups of adult dogs did not differ. Nevertheless, there are a few points to take into consideration in interpreting these findings. Although the difference between the groups was significant, whole blood taurine concentrations of individuals in the Tau– group were not severely depleted compared with cats or humans from other studies (1). It is possible that if the animals were in a greater stage of taurine depletion, the platelet results could have shown differences. Also, the range of whole blood and platelet taurine concentration was very broad, and therefore the variation was large. The variances within sample especially in the Tau+ group may have affected the ability of finding differences, when they exist. If not, the results show a difference in the role of taurine as it affects clotting among dogs vs. cats and humans.

Taurine deficient platelets do not seem to be hyper-reactive in dogs with mild taurine deficiency. Further studies with a larger number of dogs with more severe taurine deficiency are needed to determine whether there is a difference in aggregation function between taurine deficient vs. clinically normal dogs.


   FOOTNOTES
 
1 Published in a supplement to The Journal of Nutrition. Presented as part of The WALTHAM International Nutritional Sciences Symposium: Innovations in Companion Animal Nutrition held in Washington, DC, September 15–18, 2005. This conference was supported by The WALTHAM Centre for Pet Nutrition and organized in collaboration with the University of California, Davis, and Cornell University. This publication was supported by The WALTHAM Centre for Pet Nutrition. Guest editors for this symposium were D'Ann Finley, Francis A. Kallfelz, James G. Morris, and Quinton R. Rogers. Guest editor disclosure: expenses for the editors to travel to the symposium and honoraria were paid by The WALTHAM Centre for Pet Nutrition. Back

2 Author disclosure: no relationships to disclose. Back


   LITERATURE CITED
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 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 LITERATURE CITED
 

1. Hayes KC, Pronczuk A, Addesa AE, Stephan ZF. Taurine modulates platelet aggregation in cats and humans. Am J Clin Nutr. 1989;49:1211–6.[Abstract/Free Full Text]

2. National Reserch Council. Guide for the care and use of laboratory animals. Washington: National Academy Press, 1996.

3. Tôrres CL, Backus RC, Fascetti AJ, Rogers QR. Taurine status in normal dogs fed a commercial diet associated with taurine deficiency and dilated cardiomyopathy. J Anim Physiol Anim Nutr (Berl). 2003;87:359–72.[Medline]

4. Field CL, Walker NJ, Tablin F. Northern elephant seal platelets: analysis of shape change and response to platelet agonists. Thromb Res. 2001;101:267–77.[Medline]

5. Delaney SJ, Kass PH, Rogers QR, Fascetti AJ. Plasma and blood taurine in normal dogs of varying size fed commercially prepared food. J Anim Physiol Anim Nutr (Berl). 2003;87:236–44.[Medline]

6. Laidlaw SA, Sturman JA, Kopple JD. Effect of dietary taurine on plasma and blood cell taurine concentrations in cats. J Nutr. 1987;117:1945–59.[Abstract/Free Full Text]

7. Vinton NE, Laidlaw SA, Ament ME, Kopple JD. Taurine concentrations in plasma and blood cells of patients undergoing long-term parenteral nutrition. Am J Clin Nutr. 1986;44:398–404.[Abstract/Free Full Text]





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