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Red cell survival in the gerbil (Meriones unguiculatus)
Camp. Biochem. Physiol., 1972, Vol. 43A, pp. 801 to 804. Pergamon Press. Printed in Great Britain
RED CELL SURVIVAL IN THE GERBIL (MERIONES UNGUICULATUS)* JAMES
E. WOMACK
Department of Biology, Abilene Christian College, Abilene, Texas 79601 (Received 6 March 1972)
Abstract-l.
A study of the survival of erythrocytes in Merimes unguiculatus was made by measuring loss of activity from Wk-labeled cells after autotransfusion. 2. Exponential loss was observed with an “apparent” half survival time of 9.9 days. 3. This value probably reflects a true survival somewhat shorter than that found in the erythrocytes of other laboratory mammals previously studied.
INTRODUCTION
THE VALUE of the Mongolian gerbil, M&ones ung~ic&ztus, as an experimental animal has only recently been recognized (Rich, 1968). Several unique biochemical and physiological characteristics contribute to the value of this rodent in biological research. A high degree of heat tolerance and capacity for temperature regulation (Robinson, 1959), unique water metabolism (Winkelmann & Getz, 1962), resistance to radiation (Chang et al., 1964) and unusual tissue lactic dehydrogenase patterns (Karlsson & Larsson, 1971) are among the distinguishing physiological traits of this species. Although hematological parameters for the gerbil have been reported (Handler et al., 1966; Mays, 1969) erythrocyte survival data are not available. Such data are of special interest in regard to the animal’s ability to survive high doses of radiation and has likely implications in other areas of comparative physiology. Radioactive sodium chromate (Na5iCr0,) was initially used to determine “apparent” half-survival time in human red cells (Necheles et al., 1953) and has since been used to establish the same parameter in several laboratory mammals (Goodman & Smith, 1961; Kreier et al., 1970). “Apparent” half-survival (T*Cr) represents the time required for one-half the initial radioactivity to disappear from peripheral erythrocytes. It is not corrected for erythrocyte elution of 51Cr which has been found to occur at a rate of 1.3-5.9 per cent per day in other mammals (Ebaugh et al., 1953; Kreier et al., 1970). The present study reports “apparent” half-survival for the gerbil erythrocyte as determined by autotransfusion of Na51Cr0, labeled cells. # Supported by Brown-Hazen Fund of Research Corporation. 801
802
JAMESE. WOMACK MATERIALS
AND METHODS
Adult Mongolian gerbils from a strain bred in our laboratory since 1969 were used in
this study. Sixteen males (mean body weight + S.E. = 70.4 & 4.2 g) and fourteen females (mean body weight + S.E. = 61.5 rt 3.9 g) were randomly assigned to six treatment groups of five animals each. Since differences in erythrocyte survival between sexes were not found, the sexes of the animals are not included in the data herein reported. All animals were bled by heart puncture under nembutal anesthesia. After 0.5 cm3 of blood was collected from each animal, plasma was removed by centrifugation and replaced by physiological saline. Each aliquot was then incubated for 1 hr with 5 &i of Wr (Squibb Chromotope Sodium), washed once in saline, resuspended in an equal volume of saline and reinjected into the animal via the tail vein. Seven days after autotransfusion of the labeled cells, each animal was bled via the retro orbital sinus. Fifty ,ul of whole blood was collected from each animal, mixed with 0.5 ml water and frozen. These aliquots, when measured for radioactivity, were ascribed the value of 100 per cent activity. One treatment group (five animals) was then bled by the same method every 5 days for the duration of the experiment. All samples were measured for activity after the final collection in a well-type scintillation counter. RESULTS
AND DISCUSSION
Activity at S-day intervals is expressed as the percentage activity at the initial bleeding for each animal. These data are summarized in Table 1. Exponential loss of activity was indicated by regression analysis and the regression line calculated
Day
5 10 15 20 25 30
Percentage of activity at day zero (mean + S.E.) Animals
67.8 * 1.8 47.2 + l-6 35.0 + f-2 24.2 f 1.9 17.2 + 1.7 12*2* 1.7
5 5 5 5 5 5
from the logarithm of percentage activity remaining vs. days after initial bleeding for each animal is illustrated in Fig. 1. This line has a slope (b = - 0.029) which corresponds to a Tt of 9.9 days. This “apparent” half-survival value is considerably shorter than the 15-20 day values reported for rats, mice and guinea pigs (Goodman & Smith, 1961; Prouza et ai., 1970) and may reflect an unusually short erythrocyte life span or elution of the Wr label from the erythrocytes at a rate exceeding that of the other laboratory mammals. A similar “apparent” halfsurvival for the cat (Fe& catus) has been shown to be an underestimate of true survival due to label elution (Kreier et al., 1970). The value for the gerbil is very likely an underestimate of true survival but the 15-20 day values for other mammals mentioned above are also “apparent” values uncorrected for elution. The consistency of QZr elution in mammalian erytbrocytes (Ebaugh et caZ.,1953 ; Kreier
RED CELL SURVIVALIN THE GERBIL
803
1970) would suggest that these data reflect an erythrocyte life span for the gerbil that is somewhat shorter than that of the other laboratory species. Certainly the unique physiological characteristics of this mammal (especially high LD6,,_a,, to ionizing radiations) should not be attributed to an unusually long red cell life span. et al.,
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15
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Days FIG. 1. Logarithm of percentage of remaining siCr activity over a JO-day period beginning at day zero, 1 week after autotransfusion of labeled cells. REFERENCES CHANC M. C., HUNT D. M. & TURBYFILL C. (1964) High resistance of Mongolian gerbils to irradiation. Nature, Land. 203, 536-537. EBAUCH F. G., EMERSON C. P. & Ross J. F. (1953) The use of radio-active chromium-51 as an erythrocyte tagging agent for the determination of red cell survival in viva. J. clin. Invest 32, 1260-1276. GOODMANJ. W. & SMITH L. H. (1961) Erythrocyte life span in normal mice and in radiation bone marrow chimeras. Am. J. Physiol. 200, 764-770. HANDLER A. H., MAGALINI S. I. & PAV D. (1966) Oncogenic studies in the Mongolian gerbil. Cancer Res. 26, 844-847. KARLSSON B. W. & LARSSON G. B. (1971) Lactic and malic dehydrogenases and their multiple molecular forms in the Mongolian gerbil as compared with the rat, mouse and rabbit. Comp. Biochem. Physiol. 40, 93-108. KREIER J. P., SWANN I. A., TAYLOR W. M. & WAGNERW. M. (1970) Erythrocyte life span and label elution in monkeys (Macaca mulatta) and cats (Fe&s catus) determined with chromium-51 and diisopropyl fluorophosphate-32. Am.J. vet. Res. 31, 1429-1435. MAYS A. (1969) Baseline hematological and blood biochemical parameters of the Mongolian gerbil (Meriones unguiculatus). Lab. Anim. Care 19, 838-842. NECHELEST. F., WEINSTEIN I. M. & LEROY G. V. (1953) Radioactive sodium chromate for the study of survival of red blood cells-I. The effect of radioactive sodium chromate in red cells. J. Lab clin. Med. 42, 358-367. PROUZAA., POPISIL J. & DIENSTBIER 2. (1970) The survival of %r-labeled erythrocytes in dependence to the dose of whole body x-irradiation. Strahlentherapie 140, 221-230. RICH S. T. (1968) The Mongolian gerbil (Meriones unguiculatus) in research. Lab. Anim. Care 18, 235-243.
JAMESE. WOMACK
804
ROBINSONP. F. (1959) Metabolism of the gerbil, Meriones unguiculatus. Science, N.Y. 130, 502-503. WINKELMANN J. R. & GETZ L. L. (1962) Water balance in the Mongolian gerbil. g. Mammal. 43,150-154. Key Word Index-Meriones 51.
unguiculatus; gerbil; erythrocytes; RBC life span; chromium-
RED CELL SURVIVAL IN THE GERBIL (MERIONES UNGUICULATUS)* JAMES
E. WOMACK
Department of Biology, Abilene Christian College, Abilene, Texas 79601 (Received 6 March 1972)
Abstract-l.
A study of the survival of erythrocytes in Merimes unguiculatus was made by measuring loss of activity from Wk-labeled cells after autotransfusion. 2. Exponential loss was observed with an “apparent” half survival time of 9.9 days. 3. This value probably reflects a true survival somewhat shorter than that found in the erythrocytes of other laboratory mammals previously studied.
INTRODUCTION
THE VALUE of the Mongolian gerbil, M&ones ung~ic&ztus, as an experimental animal has only recently been recognized (Rich, 1968). Several unique biochemical and physiological characteristics contribute to the value of this rodent in biological research. A high degree of heat tolerance and capacity for temperature regulation (Robinson, 1959), unique water metabolism (Winkelmann & Getz, 1962), resistance to radiation (Chang et al., 1964) and unusual tissue lactic dehydrogenase patterns (Karlsson & Larsson, 1971) are among the distinguishing physiological traits of this species. Although hematological parameters for the gerbil have been reported (Handler et al., 1966; Mays, 1969) erythrocyte survival data are not available. Such data are of special interest in regard to the animal’s ability to survive high doses of radiation and has likely implications in other areas of comparative physiology. Radioactive sodium chromate (Na5iCr0,) was initially used to determine “apparent” half-survival time in human red cells (Necheles et al., 1953) and has since been used to establish the same parameter in several laboratory mammals (Goodman & Smith, 1961; Kreier et al., 1970). “Apparent” half-survival (T*Cr) represents the time required for one-half the initial radioactivity to disappear from peripheral erythrocytes. It is not corrected for erythrocyte elution of 51Cr which has been found to occur at a rate of 1.3-5.9 per cent per day in other mammals (Ebaugh et al., 1953; Kreier et al., 1970). The present study reports “apparent” half-survival for the gerbil erythrocyte as determined by autotransfusion of Na51Cr0, labeled cells. # Supported by Brown-Hazen Fund of Research Corporation. 801
802
JAMESE. WOMACK MATERIALS
AND METHODS
Adult Mongolian gerbils from a strain bred in our laboratory since 1969 were used in
this study. Sixteen males (mean body weight + S.E. = 70.4 & 4.2 g) and fourteen females (mean body weight + S.E. = 61.5 rt 3.9 g) were randomly assigned to six treatment groups of five animals each. Since differences in erythrocyte survival between sexes were not found, the sexes of the animals are not included in the data herein reported. All animals were bled by heart puncture under nembutal anesthesia. After 0.5 cm3 of blood was collected from each animal, plasma was removed by centrifugation and replaced by physiological saline. Each aliquot was then incubated for 1 hr with 5 &i of Wr (Squibb Chromotope Sodium), washed once in saline, resuspended in an equal volume of saline and reinjected into the animal via the tail vein. Seven days after autotransfusion of the labeled cells, each animal was bled via the retro orbital sinus. Fifty ,ul of whole blood was collected from each animal, mixed with 0.5 ml water and frozen. These aliquots, when measured for radioactivity, were ascribed the value of 100 per cent activity. One treatment group (five animals) was then bled by the same method every 5 days for the duration of the experiment. All samples were measured for activity after the final collection in a well-type scintillation counter. RESULTS
AND DISCUSSION
Activity at S-day intervals is expressed as the percentage activity at the initial bleeding for each animal. These data are summarized in Table 1. Exponential loss of activity was indicated by regression analysis and the regression line calculated
Day
5 10 15 20 25 30
Percentage of activity at day zero (mean + S.E.) Animals
67.8 * 1.8 47.2 + l-6 35.0 + f-2 24.2 f 1.9 17.2 + 1.7 12*2* 1.7
5 5 5 5 5 5
from the logarithm of percentage activity remaining vs. days after initial bleeding for each animal is illustrated in Fig. 1. This line has a slope (b = - 0.029) which corresponds to a Tt of 9.9 days. This “apparent” half-survival value is considerably shorter than the 15-20 day values reported for rats, mice and guinea pigs (Goodman & Smith, 1961; Prouza et ai., 1970) and may reflect an unusually short erythrocyte life span or elution of the Wr label from the erythrocytes at a rate exceeding that of the other laboratory mammals. A similar “apparent” halfsurvival for the cat (Fe& catus) has been shown to be an underestimate of true survival due to label elution (Kreier et al., 1970). The value for the gerbil is very likely an underestimate of true survival but the 15-20 day values for other mammals mentioned above are also “apparent” values uncorrected for elution. The consistency of QZr elution in mammalian erytbrocytes (Ebaugh et caZ.,1953 ; Kreier
RED CELL SURVIVALIN THE GERBIL
803
1970) would suggest that these data reflect an erythrocyte life span for the gerbil that is somewhat shorter than that of the other laboratory species. Certainly the unique physiological characteristics of this mammal (especially high LD6,,_a,, to ionizing radiations) should not be attributed to an unusually long red cell life span. et al.,
I
I
5
IO
I
15
I
20
I
25
I
30
Days FIG. 1. Logarithm of percentage of remaining siCr activity over a JO-day period beginning at day zero, 1 week after autotransfusion of labeled cells. REFERENCES CHANC M. C., HUNT D. M. & TURBYFILL C. (1964) High resistance of Mongolian gerbils to irradiation. Nature, Land. 203, 536-537. EBAUCH F. G., EMERSON C. P. & Ross J. F. (1953) The use of radio-active chromium-51 as an erythrocyte tagging agent for the determination of red cell survival in viva. J. clin. Invest 32, 1260-1276. GOODMANJ. W. & SMITH L. H. (1961) Erythrocyte life span in normal mice and in radiation bone marrow chimeras. Am. J. Physiol. 200, 764-770. HANDLER A. H., MAGALINI S. I. & PAV D. (1966) Oncogenic studies in the Mongolian gerbil. Cancer Res. 26, 844-847. KARLSSON B. W. & LARSSON G. B. (1971) Lactic and malic dehydrogenases and their multiple molecular forms in the Mongolian gerbil as compared with the rat, mouse and rabbit. Comp. Biochem. Physiol. 40, 93-108. KREIER J. P., SWANN I. A., TAYLOR W. M. & WAGNERW. M. (1970) Erythrocyte life span and label elution in monkeys (Macaca mulatta) and cats (Fe&s catus) determined with chromium-51 and diisopropyl fluorophosphate-32. Am.J. vet. Res. 31, 1429-1435. MAYS A. (1969) Baseline hematological and blood biochemical parameters of the Mongolian gerbil (Meriones unguiculatus). Lab. Anim. Care 19, 838-842. NECHELEST. F., WEINSTEIN I. M. & LEROY G. V. (1953) Radioactive sodium chromate for the study of survival of red blood cells-I. The effect of radioactive sodium chromate in red cells. J. Lab clin. Med. 42, 358-367. PROUZAA., POPISIL J. & DIENSTBIER 2. (1970) The survival of %r-labeled erythrocytes in dependence to the dose of whole body x-irradiation. Strahlentherapie 140, 221-230. RICH S. T. (1968) The Mongolian gerbil (Meriones unguiculatus) in research. Lab. Anim. Care 18, 235-243.
JAMESE. WOMACK
804
ROBINSONP. F. (1959) Metabolism of the gerbil, Meriones unguiculatus. Science, N.Y. 130, 502-503. WINKELMANN J. R. & GETZ L. L. (1962) Water balance in the Mongolian gerbil. g. Mammal. 43,150-154. Key Word Index-Meriones 51.
unguiculatus; gerbil; erythrocytes; RBC life span; chromium-