TOXICOLOGY
AND
APPLIED
Allometric
PHARMACOLOGY
Analysis
35, 543-551
of Organ
(1976)
Weights:
II. Beagle
Dogs
L. LUTZEN, G. TRIEB, AND G. PAPPRITZ Department
of Experimental
Received
Pathology,
September
Dr. Karl
16,1975;
Thomae
accepted
GmbH,
November
Biberach,
Germany
4,1975
Allometric Analysis of Organ Weights: II. Beagle Dogs. L~~TZEN, L., TRIEB, G. AND PAPPRITZ, G. (1976). Toxicol. Appl. Pharmacol. 35,543-551. A statistical analysis of organ growth was performed in 141 beagle dogs. Applying the allometric function, the correlation between organ and body weight could be described statistically. In the age range between 14 and 567 days, a significant linear, positive correlation was found between organ and body weight increase in all investigated organs, excepting the thymus. For each of the 12 organs allometric curves were established and the related tolerance limits and growth constants were calculated. In some organs sex-related differences were seen. The ratio of organ to body weight (relative organ weight) could not be described statistically as a function of age. Therefore, the use of allometric data is recommended instead of relative organ weights for the evaluation of organ weight changes.
Despite the fact that dogs are increasingly used as laboratory animals, there is a paucity of data concerning organ weights. Fielder et al. (1959), Reber et al. (1961), Jackson and Capiello (1964), Anderson and Goldman (1970), and Deavers et al. (1972) have published data on absolute and relative organ weights in the dog, but the range of biological variation was estimated only for relative organ weights. Objections were raised against the use of relative organ weights by Angervall and Carlstrom (1963) and by Mayer (1963) from a statistical point of view. Deavers et al. (1972) have also analyzed organ weights of dogs as a function of age, and they have found an almost linear correlation between the weight of the organs and that of the body. But these data are only applicable up to an age of 7 months, and neither fiducial nor tolerance limits were calculated. The present statistical analysis was performed to obtain general information on organ growth in the beagle and to establish tolerance limits for comparative work in toxicological studies. METHODS
A total of 141 beagle dogs (70 males, 71 females) was examined. The majority of the dogs had served as controls in toxicity tests. The age range was between 2 and 81 weeks (14 and 567 days), the body weight varied between 1 and 13 kg. After sacrifice, under pentobarbital anesthesia, by puncture of the abdominal aorta, the following organs were weighed: heart, lung, liver, kidney, brain, spleen, thymus, testes, ovaries, adrenal, thyroid,
pituitary.
The combined
Copyright 0 1976 by Academic Press, Inc. All rights of reproduction in any form reserved. Printed in Great Britain
543
weight
of paired organs was recorded.
544
LijTZEN,
TRIEB
AND
PAPPRITZ
The data obtained were analyzed statistically by means of a polynomial analysis and by estimation of the allometric function (Trieb et al., 1976).
regression
RESULTS
During the whole observation period, all investigated organs, excepting the thymus, showed a significant linear, positive correlation to body weight. This was proved by logarithmic transformation of the estimated allometry function of each organ. In Figs. 1-14 the estimated but retransformed allometric curves are shown for each organ together with the observed group mean values and tolerance limits (p < 0.05). The curves are displayed separately for each sex if significant sex differences exist.
heart
14-2- Igl 130 I20
-
110 100 90
-
60
-
70 60 50 40 30
-
-1
1,
I
2
I
3
8
I
4
5
I
I
I
I
6
7
8
9
I
10 body
I,
/I
,
I.2 weight
13 [kg]
FIG. 1. Regression between absolute heart weight and body weight of male dogs (u.t.l., upper tolerance limit; Lt.]., lower tolerance limit).
150
“. t 1.
140 130 120 110 100 90 / I/.
80 70 60 50 40 30 20 10 0 -i
I
I
2
I
3
I
4
I
5
I
6
I
7
I
8
I
9
,
10 body
/I
,
we/ght
I
12
I
13 lkgl
2. Regression between absolute heart weight and body weight of female dogs (u.t.I., upper tolerance limit; Lt.]., lower tolerance limit). FIG.
ANALYSIS
OF DOG
ORGAN
545
WEIGHT
Table 1 shows the specific growth constant (b) for the investigated organs in male dogs together with the tolerance limits of b and the coefficients of correlation. With the exception of testes and heart, all organs grew more slowly than the body in a negative
IL0 I30 120 110 loo 90 80 70 60 50 LO 30 20 IO 0
FIG. 3. Regression between absolute lung weight and body weight (u.t.l., upper tolerance limit; I.t.l., lower tolerance limit).
650 600 550 500 450 LOO 350 300 250 200 150 100 50 0
I
2
3
4
5
6
7
8
9
10 body
11 12 weight
13 lkgl
FIG. 4. Regression between absolute liver weight and body weight (u.t.l., upper tolerance limit; l.t.l., lower tolerance limit).
allometric way. The lowest growth rate was found for the brain (b = 0.30), whereas the testes (b = 1.78) and heart (b = 1.08) developed more rapidly than the body. However, in the testes this positive allometric growth could be observed only within the age range of 7-180 days.
546
LUTZEN, TRIEB AND PAPPRITZ
kidneys
* 9
I
I
2
3
4
5
6
7
I
I
I
8
9
IO
II
1
I
body
weight
I
12
13 lkgl
5. Regression between absolute kidney weight and body weight (u.t.l., upper tolerance limit; I.t.l., lower tolerance limit). FIG.
I I
2
I3 4
3
, 6
5
I 7
, 8
, 9
, IO
, II
, 12
body
weight
, 13 lkgl
6. Regression between absolute brain weight and body weight (u.t.l., upper tolerance limit; I.t.l., lower tolerance limit). FIG.
50 45 40 35 30 25 20 I5 10 5 0 -I
I
I
I,
I
2
3
L
5
,
,
,
,
,
,
,
,
6
7
8
9
10
11
12
13
body
weight
/kg/
7. Regression between absolute spleen weight and body weight (u.t.I., upper tolerance limit; I.t.l., lower tolerance limit). FIG.
547
ANALYSIS OF DOG ORGAN WEIGH-I
No correlation was found between the weight of the thymus and the body. Table 2 contains the same parameters for female beagles. The coefficients of correlation in males as well as in females were very high for all investigated organs, excepting the thymus.
fesfes
60. IsI
I
2
3
4
5
6
7
8
9
10
11
body
weigh
12 f [kg]
FIG. 8. Regression between absolute weight of testes and body weight (u.t.l., upper tolerance limit; l.t.l., lower tolerance limit).
200 100 2000 900 800 700 600 500 LOO 300 200 100 ,000 900 800 700 600 500 LOO 300 200 100 0
ovaries
- lwl
,
2
3
L
5
6
7
8
9
10 body
II II werght
13 lkgl
FIG. 9. Regression between absolute weight of ovaries and body weight (u.t.l., upper tolerance limit; l.t.l., lower tolerance limit).
By the model of linear covariance analysis, significant sex differences were found for heart and adrenals of male and female dogs. During the whole observation period the specific growth rate of the heart and adrenals was higher in females than in males (1.13: 1.08; 0.85:0.72).
548
LijTZEN,
TRIEB
AND
PAPPRITZ
adrenals
900
cj
800
700 600 500 LOO 300 200 100 1000 900 800
700 600 500 L 00 300 zoo 100 0
I
2
3
L
5
6
7
a
9
IO body
II
I2 weight
13 lkgl
FIG. 10. Regression between absolute adrenal weight and body weight of male:dogs (u.t.l., upper tolerance limit; I.t.l., lower tolerance limit).
200 IO0 2000 900
“. 1. 1.
a00
700 600 500 LOO 300 200 I 00 1000 900
I. I 1.
800
700 600 500 LOO 300 200 100 0 I
2
3
L
5
6
7
a
9
IO body
II 12 werght
13 [kg/
FIG. 11. Regression between absolute adrenal weight and body weight of female dogs (u.t.l., upper tolerance limit; Lt.]., lower tolerance limit).
The ratio of organ-to-body weight (relative organ weight) could not be described statistically as a function of age. As is shown in Fig. 14 using the liver as an example, significant weight differences occurred within short intervals of age which could not be interpreted biologically.
549
ANALYSIS OF DOG ORGAN WEIGHT
thyroids
8 Q
I I,
I
2
3
4
5
I
I
I
I
I
6
7
8
9
JO body
FIG. 12. Regression between absolute thyroid:weight limit; I.t.l., lower tolerance limit).
130120
pitu, itary
lmgl
I
,
I1 12 weight
I
13 /kg]
and body weight (u.t.l., upper tolerance
d 9
-
I
2
3.
3I
4,
5,
6,
7,
8,
,
,
9
10 body
,
It
I2 weight
13 Ikgl
FIG. 13. Regression between absolute pituitary weight and body weight (u.t.l., upper tolerance limit; I.t.l., lower tolerance limit).
%
liver
5.4 5.2
.
5.0 4,8 4.6
.-. r\
*
4.4
Iti .
4.2 4.0 3.8 3.6 3.4
. _ .
3.2
-
3.0
0
FIG.
weight
_.
‘i
4
8
1216202428U36404448V56M)6468727680bC8892ogc(wccks)
14. Correlation
between relative liver weight (y) and age (x), female dogs.
550
LtiTZEN,TRIEB
AND PAPPRITZ
TABLE I ALLOMETRIC GROWTH CONSTANTSOF ORGANSOF MALE BEAGLE DOGS
Organ Body weight Testes Heart Lungs Liver Adt enals Spleen Kidneys Thyroid Pituitary Brain Thymus
b
Confidence limitsb
Linear correlation coefficient
1.57-l .99 1.04-1.13 0.80-0.87 0.75-0.86 0.66-0.78 0.59*.73 0.54-0.63 0.414.55 0.384.51 0.26-0.34 -
0.97 0.99 0.98 0.96 0.94 0.92 0.96 0.86 0.85 0.88 -
1.00 1.78’ l.OSd 0.83 0.80 0.72 0.66 0.59 0.48 0.44 0.30 -
’ Allometric growth constant (b) of different organs. ’ Lower and upper confidence limits of b, p < 0.05. c Positive linear allometry in the age range of 7-180 days. d Values in bold-face type indicate significant sex differences. ALLOMETRICGROWTH
TABLE 2 CONSTANTSOF~RGANS BEAGLE Does
OFFEMALE Linear correlation
Organ
b”
Body weight Heart Lungs Adrenals Liver Ovaries Spleen Kidneys Thyroid Pituitary Brain Thymus
1 .oo 1.13’ 0.86 0.85 0.83 0.77 0.65 0.59 0.52 0.48 0.32 -
Confidence
limitsb
coefficient
1.09-1.18 0.81-0.90 0.78-0.92 0.78-0.88 0.64-0.90 0.56-0.74 0.55-0.64 0.440.60 0.39-0.58 0.28-0.36 -
0.98 0.98 0.95 0.97 0.81 0.87 0.95 0.83 0.78 0.88 -
a Allometric growth constant (6) of different organs. b Lower and upper confidence limits of 6, p < 0.05. c Values in bold-face type indicate significant sex differences. DISCUSSION
Our statistical analysis of organ growth in beagleshas revealed a continuous growth for most of the investigated organs. This pattern was maintained during the whole observation period from 2 to 81 weeks of age. We did not find definite growth phases of organs in the dog as were claimed for other species(Brody, 1945). Based on our
ANALYSIS OF DOG ORGAN WEIGHT
551
investigation, however, the existence of such growth phases cannot be excluded for the very first postnatal days or for elder animals. Otherwise, the observation of constant growth rates in the organs of dogs is in good agreement with the results obtained in rats (Trieb et al., 1976). The values of the constant b in our dogs were similar to those reported in the literature (Deavers et al., 1972). We could also demonstrate sex-related differences in the heart and adrenals. This finding is in contrast to the conclusion of Anderson and Goldman (1970) who denied such sex differences in organ weights for the dog. On the other hand, the higher growth rate of adrenals in females parallels our own findings in rats (Trieb et al., 1976). This phenomenon can be supported by some biochemical facts, which suggest a more rapid functional development of the adrenals in female rats (Glenister and Yates, 1961; Kitay, 1961). There is also evidence for a morphological substrate of this adrenal sex dimorphism (Dhom et al., 1971; Mausle, 1971). For the same reasons as were discussed for rats (Trieb et al., 1976), the absolute organ weights should be preferred for the evaluation of possible organ-specific drug effects in dogs. This is important since the number of dogs in most experiments is usually too small to allow statistical analysis on a group mean basis. REFERENCES ANDERSON, A. C. ANDGOLDMAN,M. (1970). Growth and development.In The Beagle as an Experimental Dog, pp. 83-93. Iowa State University Press,Ames, Iowa. ANGERVALL, L. ANDCARLSTR~M, E. (1963).Theoretical criteria for the useof relative organ weightsand similarratios in biology. J. Theor. Biol. 4,245-259. BRODY, S. (1945). Bioenergetics and Growth, pp. 484-663. Reinhold Publishing,New York. DEAVERS, S., HUGGINS,R. A. ANDSMITH,E. L. (1972).Absolute and relative organ weights of the growing beagle.Growth 36,195-208.
DHOM,G., v. SEEBACH, H. B. ANDSTEPHAN, G. (1971). Der Geschlechtsdimorphismus der Nebennierenrindeder Ratte. Lichtmikroskopischeund histometrischeUntersuchungen. Z. Zellforsch. 116, 119-135. FIELDER,F. G., HOFF,E. J., THOMAS,G. B., TOLKSDORF, S., PERLMAN,P. L. ANDCRONIN, M. T. I. (1959). A study of subacutetoxicity of prednisolone,methylprednisoloneand triamcinolonein dogs.Toxicol. Appl. Pharmacol. 1, 305-314. GLENISTER, D. W. AND YATES, F. E. (1961).Sex differencesin the rate of disappearanceof corticosterone-4-Cl4from plasmaof intact rats: Further evidenceof hepatic 4-steroidhydrogenaseactivity on adrenalfunction. Endocrinology 68, 747-758. JACKSON, B. AND CAPIELLO, V. P. (1964).Rangesof normal organ weightsin dogs. Toxicol. Appl. Pharmacol. 6,664-668. KITAY, J. I. (1961).Sex differencesin adrenalcortical secretionin the rat. Endocrinology
68,
818-824. M&SLE, E. (1971). Geschlechtsunterschiede in der Ultrastruktur der Nebennierenrindeder Ratte. Z. Zellforsch. 116, 136-150. MAYER, E. (1963). Introduction
to Dynamic Morphology,
pp. 485-486. Academic Press, New
York. REBER, E. F., MALHOTRA, 0. P., SIMON, J., KREIER, J. P., BEAMER, P. D. AND NORTON, H. W.
(1961). The effects of feeding irradiated flour to dogs. II. Reproduction and pathology. Toxicol. Appl. Pharmacol. 3,568-573. TRIEB, G., PAPPRITZ, G. AND L~TZEN,L. (1976).Allometric analysisof organweights:I. Rats. Toxicol. Appl. Pharmacol., 35, 531-542.
AND
APPLIED
Allometric
PHARMACOLOGY
Analysis
35, 543-551
of Organ
(1976)
Weights:
II. Beagle
Dogs
L. LUTZEN, G. TRIEB, AND G. PAPPRITZ Department
of Experimental
Received
Pathology,
September
Dr. Karl
16,1975;
Thomae
accepted
GmbH,
November
Biberach,
Germany
4,1975
Allometric Analysis of Organ Weights: II. Beagle Dogs. L~~TZEN, L., TRIEB, G. AND PAPPRITZ, G. (1976). Toxicol. Appl. Pharmacol. 35,543-551. A statistical analysis of organ growth was performed in 141 beagle dogs. Applying the allometric function, the correlation between organ and body weight could be described statistically. In the age range between 14 and 567 days, a significant linear, positive correlation was found between organ and body weight increase in all investigated organs, excepting the thymus. For each of the 12 organs allometric curves were established and the related tolerance limits and growth constants were calculated. In some organs sex-related differences were seen. The ratio of organ to body weight (relative organ weight) could not be described statistically as a function of age. Therefore, the use of allometric data is recommended instead of relative organ weights for the evaluation of organ weight changes.
Despite the fact that dogs are increasingly used as laboratory animals, there is a paucity of data concerning organ weights. Fielder et al. (1959), Reber et al. (1961), Jackson and Capiello (1964), Anderson and Goldman (1970), and Deavers et al. (1972) have published data on absolute and relative organ weights in the dog, but the range of biological variation was estimated only for relative organ weights. Objections were raised against the use of relative organ weights by Angervall and Carlstrom (1963) and by Mayer (1963) from a statistical point of view. Deavers et al. (1972) have also analyzed organ weights of dogs as a function of age, and they have found an almost linear correlation between the weight of the organs and that of the body. But these data are only applicable up to an age of 7 months, and neither fiducial nor tolerance limits were calculated. The present statistical analysis was performed to obtain general information on organ growth in the beagle and to establish tolerance limits for comparative work in toxicological studies. METHODS
A total of 141 beagle dogs (70 males, 71 females) was examined. The majority of the dogs had served as controls in toxicity tests. The age range was between 2 and 81 weeks (14 and 567 days), the body weight varied between 1 and 13 kg. After sacrifice, under pentobarbital anesthesia, by puncture of the abdominal aorta, the following organs were weighed: heart, lung, liver, kidney, brain, spleen, thymus, testes, ovaries, adrenal, thyroid,
pituitary.
The combined
Copyright 0 1976 by Academic Press, Inc. All rights of reproduction in any form reserved. Printed in Great Britain
543
weight
of paired organs was recorded.
544
LijTZEN,
TRIEB
AND
PAPPRITZ
The data obtained were analyzed statistically by means of a polynomial analysis and by estimation of the allometric function (Trieb et al., 1976).
regression
RESULTS
During the whole observation period, all investigated organs, excepting the thymus, showed a significant linear, positive correlation to body weight. This was proved by logarithmic transformation of the estimated allometry function of each organ. In Figs. 1-14 the estimated but retransformed allometric curves are shown for each organ together with the observed group mean values and tolerance limits (p < 0.05). The curves are displayed separately for each sex if significant sex differences exist.
heart
14-2- Igl 130 I20
-
110 100 90
-
60
-
70 60 50 40 30
-
-1
1,
I
2
I
3
8
I
4
5
I
I
I
I
6
7
8
9
I
10 body
I,
/I
,
I.2 weight
13 [kg]
FIG. 1. Regression between absolute heart weight and body weight of male dogs (u.t.l., upper tolerance limit; Lt.]., lower tolerance limit).
150
“. t 1.
140 130 120 110 100 90 / I/.
80 70 60 50 40 30 20 10 0 -i
I
I
2
I
3
I
4
I
5
I
6
I
7
I
8
I
9
,
10 body
/I
,
we/ght
I
12
I
13 lkgl
2. Regression between absolute heart weight and body weight of female dogs (u.t.I., upper tolerance limit; Lt.]., lower tolerance limit). FIG.
ANALYSIS
OF DOG
ORGAN
545
WEIGHT
Table 1 shows the specific growth constant (b) for the investigated organs in male dogs together with the tolerance limits of b and the coefficients of correlation. With the exception of testes and heart, all organs grew more slowly than the body in a negative
IL0 I30 120 110 loo 90 80 70 60 50 LO 30 20 IO 0
FIG. 3. Regression between absolute lung weight and body weight (u.t.l., upper tolerance limit; I.t.l., lower tolerance limit).
650 600 550 500 450 LOO 350 300 250 200 150 100 50 0
I
2
3
4
5
6
7
8
9
10 body
11 12 weight
13 lkgl
FIG. 4. Regression between absolute liver weight and body weight (u.t.l., upper tolerance limit; l.t.l., lower tolerance limit).
allometric way. The lowest growth rate was found for the brain (b = 0.30), whereas the testes (b = 1.78) and heart (b = 1.08) developed more rapidly than the body. However, in the testes this positive allometric growth could be observed only within the age range of 7-180 days.
546
LUTZEN, TRIEB AND PAPPRITZ
kidneys
* 9
I
I
2
3
4
5
6
7
I
I
I
8
9
IO
II
1
I
body
weight
I
12
13 lkgl
5. Regression between absolute kidney weight and body weight (u.t.l., upper tolerance limit; I.t.l., lower tolerance limit). FIG.
I I
2
I3 4
3
, 6
5
I 7
, 8
, 9
, IO
, II
, 12
body
weight
, 13 lkgl
6. Regression between absolute brain weight and body weight (u.t.l., upper tolerance limit; I.t.l., lower tolerance limit). FIG.
50 45 40 35 30 25 20 I5 10 5 0 -I
I
I
I,
I
2
3
L
5
,
,
,
,
,
,
,
,
6
7
8
9
10
11
12
13
body
weight
/kg/
7. Regression between absolute spleen weight and body weight (u.t.I., upper tolerance limit; I.t.l., lower tolerance limit). FIG.
547
ANALYSIS OF DOG ORGAN WEIGH-I
No correlation was found between the weight of the thymus and the body. Table 2 contains the same parameters for female beagles. The coefficients of correlation in males as well as in females were very high for all investigated organs, excepting the thymus.
fesfes
60. IsI
I
2
3
4
5
6
7
8
9
10
11
body
weigh
12 f [kg]
FIG. 8. Regression between absolute weight of testes and body weight (u.t.l., upper tolerance limit; l.t.l., lower tolerance limit).
200 100 2000 900 800 700 600 500 LOO 300 200 100 ,000 900 800 700 600 500 LOO 300 200 100 0
ovaries
- lwl
,
2
3
L
5
6
7
8
9
10 body
II II werght
13 lkgl
FIG. 9. Regression between absolute weight of ovaries and body weight (u.t.l., upper tolerance limit; l.t.l., lower tolerance limit).
By the model of linear covariance analysis, significant sex differences were found for heart and adrenals of male and female dogs. During the whole observation period the specific growth rate of the heart and adrenals was higher in females than in males (1.13: 1.08; 0.85:0.72).
548
LijTZEN,
TRIEB
AND
PAPPRITZ
adrenals
900
cj
800
700 600 500 LOO 300 200 100 1000 900 800
700 600 500 L 00 300 zoo 100 0
I
2
3
L
5
6
7
a
9
IO body
II
I2 weight
13 lkgl
FIG. 10. Regression between absolute adrenal weight and body weight of male:dogs (u.t.l., upper tolerance limit; I.t.l., lower tolerance limit).
200 IO0 2000 900
“. 1. 1.
a00
700 600 500 LOO 300 200 I 00 1000 900
I. I 1.
800
700 600 500 LOO 300 200 100 0 I
2
3
L
5
6
7
a
9
IO body
II 12 werght
13 [kg/
FIG. 11. Regression between absolute adrenal weight and body weight of female dogs (u.t.l., upper tolerance limit; Lt.]., lower tolerance limit).
The ratio of organ-to-body weight (relative organ weight) could not be described statistically as a function of age. As is shown in Fig. 14 using the liver as an example, significant weight differences occurred within short intervals of age which could not be interpreted biologically.
549
ANALYSIS OF DOG ORGAN WEIGHT
thyroids
8 Q
I I,
I
2
3
4
5
I
I
I
I
I
6
7
8
9
JO body
FIG. 12. Regression between absolute thyroid:weight limit; I.t.l., lower tolerance limit).
130120
pitu, itary
lmgl
I
,
I1 12 weight
I
13 /kg]
and body weight (u.t.l., upper tolerance
d 9
-
I
2
3.
3I
4,
5,
6,
7,
8,
,
,
9
10 body
,
It
I2 weight
13 Ikgl
FIG. 13. Regression between absolute pituitary weight and body weight (u.t.l., upper tolerance limit; I.t.l., lower tolerance limit).
%
liver
5.4 5.2
.
5.0 4,8 4.6
.-. r\
*
4.4
Iti .
4.2 4.0 3.8 3.6 3.4
. _ .
3.2
-
3.0
0
FIG.
weight
_.
‘i
4
8
1216202428U36404448V56M)6468727680bC8892ogc(wccks)
14. Correlation
between relative liver weight (y) and age (x), female dogs.
550
LtiTZEN,TRIEB
AND PAPPRITZ
TABLE I ALLOMETRIC GROWTH CONSTANTSOF ORGANSOF MALE BEAGLE DOGS
Organ Body weight Testes Heart Lungs Liver Adt enals Spleen Kidneys Thyroid Pituitary Brain Thymus
b
Confidence limitsb
Linear correlation coefficient
1.57-l .99 1.04-1.13 0.80-0.87 0.75-0.86 0.66-0.78 0.59*.73 0.54-0.63 0.414.55 0.384.51 0.26-0.34 -
0.97 0.99 0.98 0.96 0.94 0.92 0.96 0.86 0.85 0.88 -
1.00 1.78’ l.OSd 0.83 0.80 0.72 0.66 0.59 0.48 0.44 0.30 -
’ Allometric growth constant (b) of different organs. ’ Lower and upper confidence limits of b, p < 0.05. c Positive linear allometry in the age range of 7-180 days. d Values in bold-face type indicate significant sex differences. ALLOMETRICGROWTH
TABLE 2 CONSTANTSOF~RGANS BEAGLE Does
OFFEMALE Linear correlation
Organ
b”
Body weight Heart Lungs Adrenals Liver Ovaries Spleen Kidneys Thyroid Pituitary Brain Thymus
1 .oo 1.13’ 0.86 0.85 0.83 0.77 0.65 0.59 0.52 0.48 0.32 -
Confidence
limitsb
coefficient
1.09-1.18 0.81-0.90 0.78-0.92 0.78-0.88 0.64-0.90 0.56-0.74 0.55-0.64 0.440.60 0.39-0.58 0.28-0.36 -
0.98 0.98 0.95 0.97 0.81 0.87 0.95 0.83 0.78 0.88 -
a Allometric growth constant (6) of different organs. b Lower and upper confidence limits of 6, p < 0.05. c Values in bold-face type indicate significant sex differences. DISCUSSION
Our statistical analysis of organ growth in beagleshas revealed a continuous growth for most of the investigated organs. This pattern was maintained during the whole observation period from 2 to 81 weeks of age. We did not find definite growth phases of organs in the dog as were claimed for other species(Brody, 1945). Based on our
ANALYSIS OF DOG ORGAN WEIGHT
551
investigation, however, the existence of such growth phases cannot be excluded for the very first postnatal days or for elder animals. Otherwise, the observation of constant growth rates in the organs of dogs is in good agreement with the results obtained in rats (Trieb et al., 1976). The values of the constant b in our dogs were similar to those reported in the literature (Deavers et al., 1972). We could also demonstrate sex-related differences in the heart and adrenals. This finding is in contrast to the conclusion of Anderson and Goldman (1970) who denied such sex differences in organ weights for the dog. On the other hand, the higher growth rate of adrenals in females parallels our own findings in rats (Trieb et al., 1976). This phenomenon can be supported by some biochemical facts, which suggest a more rapid functional development of the adrenals in female rats (Glenister and Yates, 1961; Kitay, 1961). There is also evidence for a morphological substrate of this adrenal sex dimorphism (Dhom et al., 1971; Mausle, 1971). For the same reasons as were discussed for rats (Trieb et al., 1976), the absolute organ weights should be preferred for the evaluation of possible organ-specific drug effects in dogs. This is important since the number of dogs in most experiments is usually too small to allow statistical analysis on a group mean basis. REFERENCES ANDERSON, A. C. ANDGOLDMAN,M. (1970). Growth and development.In The Beagle as an Experimental Dog, pp. 83-93. Iowa State University Press,Ames, Iowa. ANGERVALL, L. ANDCARLSTR~M, E. (1963).Theoretical criteria for the useof relative organ weightsand similarratios in biology. J. Theor. Biol. 4,245-259. BRODY, S. (1945). Bioenergetics and Growth, pp. 484-663. Reinhold Publishing,New York. DEAVERS, S., HUGGINS,R. A. ANDSMITH,E. L. (1972).Absolute and relative organ weights of the growing beagle.Growth 36,195-208.
DHOM,G., v. SEEBACH, H. B. ANDSTEPHAN, G. (1971). Der Geschlechtsdimorphismus der Nebennierenrindeder Ratte. Lichtmikroskopischeund histometrischeUntersuchungen. Z. Zellforsch. 116, 119-135. FIELDER,F. G., HOFF,E. J., THOMAS,G. B., TOLKSDORF, S., PERLMAN,P. L. ANDCRONIN, M. T. I. (1959). A study of subacutetoxicity of prednisolone,methylprednisoloneand triamcinolonein dogs.Toxicol. Appl. Pharmacol. 1, 305-314. GLENISTER, D. W. AND YATES, F. E. (1961).Sex differencesin the rate of disappearanceof corticosterone-4-Cl4from plasmaof intact rats: Further evidenceof hepatic 4-steroidhydrogenaseactivity on adrenalfunction. Endocrinology 68, 747-758. JACKSON, B. AND CAPIELLO, V. P. (1964).Rangesof normal organ weightsin dogs. Toxicol. Appl. Pharmacol. 6,664-668. KITAY, J. I. (1961).Sex differencesin adrenalcortical secretionin the rat. Endocrinology
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(1961). The effects of feeding irradiated flour to dogs. II. Reproduction and pathology. Toxicol. Appl. Pharmacol. 3,568-573. TRIEB, G., PAPPRITZ, G. AND L~TZEN,L. (1976).Allometric analysisof organweights:I. Rats. Toxicol. Appl. Pharmacol., 35, 531-542.
