Cony. Biochem. Physiol. Vol. IOIA, No. 4, pp. 807-812, 1992 Printed in Great Britain

0300-9629/92 $5.00 + 0.00 0 1992 Pergamon Press plc

HEMATOLOGIC AND BLOOD CHEMISTRY DATA FOR THE PRAIRIE DOG (CYNOMYS LUDOVK’MVUS) GEORGE BROUGHTON II

Department of Biomedical Sciences, Division of Biochemistry, Creighton University School of Medicine, Omaha, NE 68178, U.S.A. Telephone: 402 280 2917 (Received 5 July 1991) Abstract-l. The prairie dog has been used extensively for the study of gallstone genesis and gallstone dissolution therapies, and has recently been implicated in an effort to prevent total parenteral nutritionassociated cholelithiasis with intravenous chenodeoxycholate. 2. Towards this effort, it is important that a range of normal blood chemistry values be reported for the prairie dog. This paper reports the mean values for a complete blood cell count, electrolytes, blood urea nitrogen, creatinine, calcium, phosphorus, liver enzymes, total bilirubin, protein, albumin, cholesterol, triglycerides and lipids for 45 adult prairie dogs. 3. The prairie dog has normochromic, microcytic blood with an increased number of red blood cells. The prairie dog also has a high concentration of small platelets. 4. The prairie dog has a higher CO, concentration with a slightly increased potassium concentration than is found in man. The anion gap is 12 with a calculated serum osmolality of 316. The BUN concentration is elevated with a 3-fold increase in the AST concentration. 5. The prairie dog has lower serum values for cholesterol, VLDL and LDL cholesterol than man. In the prairie dog, HDL cholesterol consists of 67% of the total cholesterol concentration and the LDL and HDL ratio is 0.3.

INTRODUCITON

Prairie dogs are burrowing squirrels with short legs, short tail, and a stout body. These rodents are smaller than marmots but larger than ground squir-

rels. Prairie dogs are primarily herbivores and seedeaters, and are equipped with internal cheek pouches. Like all rodents, prairie dogs have keen senses, especially hearing and smell. Prairie dogs were first collected by Lewis and Clark, and described by George Ord as a species of marmot and given the scientific name Arctomys ludovicianus-the marmot of Louisiana Territory. The naturalist Rafinesque proposed the generic name Cynomys in 18 17. Cynomys means dog-like mouse inspired by the prairie dog’s distinctive barking. Prairie dogs are divided into two groups-the black-tailed prairie dogs (subgenus Cynomys) and the white-tailed prairie dogs (subgenus Leucocrossuromys) (MacClintock, 1970). The black-tailed prairie dog (Cynomys ludooiciunus) was used in this study. Patton et al. (1961) first reported the potential for prairie dogs and ground squirrels to form cholesterol gallstones when fed a 50% egg yolk/50% monkey ration diet. This finding remained dormant for eleven years until it was reawakened when Brennenman and co-workers (1972) published their work on the characterization of the bile and the cholesterol gallstones formed in prairie dogs receiving dietary cholesterol. Today, the prairie dog is the animal model of choice for biliary studies. The prairie dog’s biliary anatomy and biliary lipid composition is almost identical to man’s. Unlike other animal models that require tremendously large doses of cholesterol, prairie dogs will form cholesterol gall-

stones within 2 weeks when fed a pure egg-yolk diet (Broughton et al., 1990). The prairie dog has been used extensively for the study of gallstone genesis and gallstone dissolution therapies, and has recently been implicated in an effort to prevent total parenteral nutrition-associated cholelithiasis with intravenous chenodeoxycholate (Broughton et al., 1991). Towards this effort, it is important that a range of normal blood chemistry values be reported for the prairie dog. This paper reports the mean values for a complete blood cell count, electrolytes, blood urea nitrogen, creatinine, calcium, phosphorus, liver enzymes, total bilirubin, protein, albumin, cholesterol, triglycerides and lipids for the prairie dog. MATERIALS

AND METHODS

Forty-five adult prairie dogs (Cynomys ludovicianus),each weighing approximately 1 kg were purchased from Mr Otto Marten Locke of New Braunfels. TX. The animals were caged in a therrnoregulated room (23°C) with 12 hr daylight cycles and were allowed free access to water and normal rat chow (Purina Laboratory Chow, Ralston Purina, St Louis, MO) for a 2 week adjustment period. Prairie dogs selected for surgery were fasted for 2-4 hr. Surgical procedures The animals were anesthetized with 100 mg of ketamine and 15 mg of xylazine intramuscularly and given 250,000 units of penjcillin-G intramuscularly approximately 30 min pre-operatively. A 22-gauge silastic tube (IO.025 x 0.047 x 0.01 1’7A-M Systems, Everett, WA) filled with normal saline was introduced into the external jugular vein and threaded to the superior vena cava-right atrium junction. Approximately 1 cc of normal saline (without heparin) was used to flush the catheter and then approximately 0.5~

807

GFCJRGE BROUOHT~N II

I

i

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809

Blood chemistry data for the prairie dog la*

I. List of dir&al serolo&ai analytes investigaxi

Hcmatofoav*

Blood chem&.ries~

White bfood c&l count (WE) Red blood 0~11count (RBC)

Carbon dioxide [Co, )

Hemoglobin concentration Hematocrit Mean cell valume (MCV) Mean cellular hemoglobin (MCH) Mean cellular hemoglobin concentration Red cell distribution width (RDW) Platelet concentration Mean &at&t volume (MPV) WEC di&rentialt

(MCHC)

Chloride Sodium Potassium Glucose Blood urea nitrogen (BUN) Creatinine Calcium Phosphorus Alkaline phasphatase (Alk Phos) Aspartate transaminase (AST) Alanine transaminase (ALTf ~-GiutamyI transpeptidase (GGTP) Total bilirubin Protein Albumin Cholesterol Triglycerides HDL cholesterolj VLDL cholesterolll LDL chotesterolll

*M~s~r~ents were made on Couiter S-PLUS STKR, coultcr Eltctronics, Miami Lakes, FL. fThe differential was performed manually. $Measurements were made on an Ektachem XWtXRAnaiyser, Eastman Kodak Company, Rochester, NV. §HDL quantitative was made by preparing the serum with a dextran suifate/ma~ium p&pit&ion with HDL cholesterol precipitating nagent tubes (Canyon Diagnostics Inc., Anaheim, CA) followed by cholesterol analysis of the supernate on the Ektachem 700XR Analyser. IlVLDL cholesterol was calculated by dividing the triglyceride concentration by 5. ILDL cholesterol = total cholesterol - (HDL + VLDL). of blood was collected in the syringe. A new syringe was exchanged for the first, and 4mI of bfood was eoflected. The silastic catheter was then Bushed with 4 ml of normal saline with 5 units/cc of heparin. One and 0.5 ml of whole blood was placed in a Vacutainer blood collection tube with EDTA additive (Becton Dickinson, Rutherford, NJ) and was used for completE blood cell count analysir and differential. The balance of blood was placed in a Vacutainer blood collection tube without additive (Becton Dickinson, Rutherford, NJ) and was used for the remaining blood chemistry tests. Table 1 lists the serological analytes studied. All measurements were made at St Joseph Hospital at Creighton University Medical Center by independent technicians. The values for the complete blood count were measured by a Coulter S-PLUS STKR (Coulter I&ctronics, Miami Lakes, FL), The differential was performed manually. The balance of analytes were measured on an Ektachem 700XR Analyser (Eastman Kodak Company, Rochester, NY). The quantitative analysis for high density lipoprotein (HDL) cholesterol was made by precipitating

the very low density lipoprotein (VLDL) and low density Iipoprotein (LDL) cholesterols with a d&ran sulfate/ magnesium reagent in manufactuti tubes(Canyon Diagno&s, Anaheim, CA) followed by a cholesterol analysis of the supemate. VLDL cholesterol was calculated by dividing the triglyceride concentration by 5. The calculation is valid for triglyceride levels less than 400 mg/dl. LDL cholesterol was then calculatsd by the following formula: LDL cholesterol = Total cholesterol - (HDL c VLDL). RESULTS

Table 2 lists the mean value f standard deviation (SD) and the normal range for the hematology variants in the prairie dog. The normal reference range from the laboratories at St Joseph Hospital at Creighton University Medical Center is included for comparison. The prairie dog red blood cell is

Tabie 2. Hematology values for the prairie dog Prairie dog Variable (units) WBC (lO’p1) RBC (106pl) Hemoglobin (g/d]) Hematocrit (%) MCV (pm’) MCW (pg) MCHC (g/dl) RDW (%f Platelet f x $0’) MPV (&m-3) Neutrophils (103) Lymphocytes (IOf) Monocytes (10’) Eosinoohils (IO’)

Range+

Mean value?

Rawer

4&l 1.a 4.60-6.00 13.5-17.5 42.0-52.0 80.0-100.0 27.0-3 1.0 32.Q35.9 11.5-15.5 I30-4w 7.4-10.4 1.4-7.5

6.3 * 1.9 6.59 f 1.1 12.0 + 2.0 36.5 + 7.0 55.1 f 5.2 18.5 + 1.9 33.5 f 2.2 17.9 * 7.5 466.2 f 156.5 6.t & 0.7 3.9 _t 1.6 2.2 -t 0.9 0.13 to.11 0.10+0.13

3.3-10.5 3.17-8.05 6.4-14.8 14.8-46.8 44.2-68.2 12.5-27.9 31.4-44.0

I .c-s.0 0.1-1.2 O-4.3

11.6-38.8 f 38-783 5.0-7.5 0.8-7.9 1.o-5.6 (r0.42 w3.50

*Represents normal reference range from the laboratories at St Yoseph Hospital at Creighton University Medical Center. t&an f SD (N = 45). ZRepresents the normal range of values for the prairie dog.

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GEORGEBROUGHTON II

normochromic microcytic, and this is clearly reflected in the red blood cell indices with a high RDW and a normal MCHC. The platelets in the prairie dog are small and numerous as indicated by a high platelet count and a small MPV. The WBC differential is comparable to that found in man. The prairie dog does have a lower absolute concentration of monocytes. Table 3 lists the mean (*SD) values for the blood analytes plus the normal high and low range in the prairie dog. The normal reference range from the laboratories at St Joseph Hospital at Creighton University Medical Center is included for comparison. When the mean values from the prairie dog are compared to the normal reference range of values for man, only the chloride, sodium, calcium, alkaline phosphatase, ALT, GGTP, total bilirubin, triglycerides and HDL cholesterol concentrations fall within this range. The frequency of distribution for the anions and the cations in the prairie dog are depicted in Fig. 1. These graphs show that sodium, potassium, chloride, and total CO, are symmetrically distributed. Figure 2 shows the symmetrical frequency of distribution for glucose. Figure 3 depicts the frequency of distribution of values for calcium, phosphorus, BUN and creatinine. The values for calcium are symmetrically distributed. The values for phosphorus and BUN exhibits a bimodal and trimodal distribution, respectively. The distribution of values for creatinine are skewed with a peak frequency at a concentration of 0.48-0.53 mg/dl. The frequency of distribution for the liver enzymes and serum lipids are shown in Figs 4 and 5, respectively. DISCUSSION

The prairie dog has a low cellular hemoglobin concentration in a small RBC. The expected decrease in oxygen carrying capacity is compensated by

GLUCOSE

Fig. 2. The frequency of distribution of variants for glucose in the prairie

dog (N = 45).

the increase in the RBC concentration. The MCV is markedly decreased with an increased RBC concentration and a low normal hemoglobin. The prairie dog has a higher CO2 concentration and a slightly increased potassium concentration. None of the samples used in this study were reported as hemolysed. The anion gap is 12, indicating a normal balance of blood anions and cations. The calculated serum osmotic concentration is dependent on the principal solutes of sodium, chloride, and bicarbonate ions, and to a lesser degree glucose and urea. The calculated serum osmolality is 3 16 mOsm/l, which is significantly greater than the highest normal value for man. These differences may explain how the prairie dog is capable of retaining metabolic water with their higher serum osmolality, decreasing their need for exogenous water (MacClintock, 1970). The author cautions the reader about making too many conclusions about the high blood glucose level reported in this paper. These animals only had a 2-4 hr fast, the equivalent amount of time one needs to collect hepatic bile from a cannulated common bile duct. These values then become more useful for

Table 3. Blood chemistry values for the prairie dog Prairie dog Variable (units)

CO, (mEs/I) Chloride (mEq/l) Sodium (mEq/l) Potassium (mEq/l) Glucose (mg/dl) BUN (mg/dl) Creatinine (mg/dl) Calcium (mg/dl) Phosphorus (mg/dl) Alk phos (IUJI) Ast (W/l) ALT (W/I) GGTP (W/l) Total bilirubin (mg/dl) Protein (g/dl) Albumin (g/dl) Cholesterol (mg/dl) Triglycerides (mg/dl) HDL cholesterol (mg/dl) VLDL cholesterol (mg/dl) LDL cholesterol (mg/dl)

Range*

24-30 96106 135-145 3.5-5.0 70-115 9-2 1 0.7-1.5 8.5-10.5 2.24.5 42-122 7-39 2-54 8-78 0.2-1.1 6.2-8.4 3.74.7 120-200 IO-190 27-72

Mean value?

Ranget

33.8 + 4.0

2243

97.6 + 4.4 143.4 k 4.2 5.1 + 1.0 317.7 k 89.6 32.0 k 7.4 0.54 i_ 0.17 9.1 * 0.4 6.3 k 0.9 73.7 * 22. I 74.9 k 29.3 25.0 ? 16.2 10.1 * 1.2 0.34 + 0.36 5.7 + 0.8 2.5 + I.1 104.0 + 25.8 59.6 + 37.6 69.9 k 14.6 11.9i7.6 20.5 ? 12.0

85-108 134-153 3.68.0 138-510 l74l 0.3-0.9 7.5-10.2 4.1-8.3 45-128 28-141 2.9-84 8-13 0.05-2.0 4.68.8 I .l-9 50-171 l&l42 46-106 3-28 345

*Represents normal reference range from the laboratories Creighton University Medical Center. tMean value k SD (IV = 45) for the prairie dog. $Observed normal range of values for the prairie dog.

at St Joseph Hospital at

Blood chemistry data for the prairie dog

r

811

812

liver

Lipid Distribution _&A /,~.------~

Enzyme Distributjon

Fig. 4. The frequency of distribution of variants for the liver enzymes in the prairie dog (N = 45).

Fig. 5. The frequency of distribution of variants for serum lipids and triglycerides in the prairie dog (N = 4.5).

comparing future measurements of blood glucose in prairie dogs receiving T.P.N. and have their blood sample drawn by an intracordial stick at the end of the bile collection. The prairie dog has almost a 3-fold elevation in aspartate aminotransferase (AST) levels than in man. This enzyme catalyses the reaction:

ent intravenous model.

and oral drugs have on this animal

Acknowledgements-The

author wishes to thank Dr Robert S. Cox, Director of Laboratories at Saint Joseph Hospital at Creighton University Medical Center, and all of his knowledgeable staff for their generous support and encouragement during the duration of this study.

aspartate -t or-ketoglutarate 9 oxaloacetate + glutamate. Aspartate is required for the production of urea in the urea cycle, and the prairie dog also has a significantly elevated blood urea nitrogen. Perhaps the increased activity of AST in the prairie dog plays an important role in maintaining a higher serum osmolality. The remaining liver enzymes, alkaline phosphatase, GGTP, and ALT, have serum levels equivalent to man. The prairie dog has lower serum levels of protein and albumin, as compared with man. The prairie dog has a lower serum value for cholesterol than man. The absolute HDL cholesterol levels are similar between the two species; however, in the prairie dog, HDL makes up 67% of the total cholesterol-compared with 26% in man (Schaefer, 1987). The VLDL and LDL cholesterols comprise 11.5 and 20% of the total cholesterol, respectively. In man, VLDL and LDL cholesterols comprise 8.5 and 65.1% of the total cholesterol, respectively (Schaefer, 1987). The LDL to HDL ratio for the prairie dog is 0.3, admirabie by any standard. This study has provided useful baseline data for the normal chemical and cellular composition of prairie dog blood. This information will prove to be valuable when future investigations examine the effect differ-

REFERENCE

Brenneman D. E., Connor W. E., Forker E. L. and DenBensten L. (1972) The formation of abnormal bile and cholesterol gallstones from dietary cholesterol in the prairie dog. J. clin. Inoest. 51, 1495-1503. Broughton G. II, Tseng A., Fitzgibbons R. Jr, Fishkin A. F. and Rongone E. L. (1990) The quantitative and qualitative analysis for biliary lipids in the prairie dog (Cynomys ludovicianus). Camp. Bioekem. Pkysiol. 97B, 521-526.

Broughton G. II, Tseng A., Fitzgibbons R. Jr, Tyndall S., Stanislav G. and Rongone E. L. (1991) The prevention of cholelithiasis with infused sodium chenodeoxycholate in the prairie dog (Cynomys ludovicianus). Comp. Biockem. Pkysiol. 99A, 605-6 13. MacClintock D. (1970) Squirrels of North America, pp. 20-32. Van Nostrand Reinhold Company, New York. Patton D. E., Plotner K., Cox G. E. and Taylor C. B. (1961) Biliary cholesterol deposits in ground squirrels and prairie dogs. Fed. Proc. M, 248A. Schaefer E. J. (1987) Premature coronary artery disease and genetic HDL deficiency. In Dyslipoproteinemia and Coronary Disease: The Significance of HDL-Cholesterol,

pp. 36-41. Proceedings of a symposium, Washington, DC, 14 September 1986. Warner-Lambert Company, Morris Planes, NJ.

Hematologic and blood chemistry data for the prairie dog (Cynomys ludovicianus).

1. The prairie dog has been used extensively for the study of gallstone genesis and gallstone dissolution therapies, and has recently been implicated ...
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