Biochemical parameters of blood plasma of the harp seal Pagophilus ...

ISSN 00220930, Journal of Evolutionary Biochemistry and Physiology, 2007, Vol. 43, No. 3, pp. 305—309. © Pleiades Publishing, Ltd., 2007. Original Russian Text © I. A. Erokhina, 2007, published in Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, 2007, Vol. 43, No. 3, pp. 254—257.

COMPARATIVE AND ONTOGENIC BIOCHEMISTRY

Biochemical Parameters of Blood Plasma of the Harp Seal Pagophilus groenlandicus Erxleben, 1777 (Pinnipedia, Procidae) of Various Ages I. A. Erokhina Murmansk Marine Biological Institute, Kola Research Center, Russian Academy of Sciences, Murmansk, Russia Received July 5, 2006

Abstract—Results of study of several blood biochemical parameters of the harp seal Pagophilus groen landicus Erxleben, 1777, from birth to the adult state are presented. The following age groups of the animals have been studied—newborns, 1.5–2 months, 1 year, 2 years, 3 years, and adults (older than 6 years). The content of total protein and its fractions, free amine nitrogen, urea, creatinine, glucose, total lipids, total calcium, and inorganic phosphorus was determined in the seal blood plas ma. Differences of the degree of expression of levels of all studied parameters in the course of early postnatal ontogenesis of the animals have been established. The most significant metabolic changes in the harp seals were revealed at the period of end of weaning and transition to independent inges tion and then after the first year of life. DOI: 10.1134/S0022093007030040 Key word: pinnipeds, age, blood plasma.

INTRODUCTION The harp seal at present is considered to be one of bioindicators of the state of the Barents Sea ec osystem [1]. Studies of this species mainly involved several aspects of its biology—distribution, migra tions, reproduction, and morphology. Biochemi cal approach in populational studies of the White Sea harp seal has been practically not developed. At the same time, ecologobiochemical monitor ing can be of unique importance for evaluation of changes in the animal metabolism, which occur, as a rule, before the appearance of morphological and populational deviations from norm [2]. This allows using it for the early diagnostics of changes taking place in water reservoir. Since the effect of environmental factors to the considerable degree depends on the organism developmental stage, the

ontogenetic principle is an integral part of the sys tem of ecologobiochemical monitoring. Taking the aboveexposed into account, the goal of the present work was to study peculiarities of several biochemical parameters in the White Sea harp seal of various ages—from newborns to adult individuals. MATERIAL AND METHODS The material for the study was blood plasma of the harp seal (Pagophilus groenlandicus Erxleben, 1777) from the White Sea population. The blood from newborn, moulted (the age of 1.5–2 months) individuals, and adult animals was obtained dur ing the hunting at the White Sea. Group of adult seals was composed of animals with the typical harp coloration as well as with the body size peculiar to

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Table 1. The total protein content and distribution of its fractions in the blood plasma of the harp seals of different ages Age, the number of animals

Protein fractions (relat. %)

Total protein (g/l)

albumin

αglobulins

βglobulins

γglobulins

Newborns, 19

78.38 ± 2.59

64.01 ± 1.75

11.08 ± 2.68

10.47 ± 2.13

14.44 ± 1.69

1.5–2 months, 16

66.96 ± 2.39*

59.50 ± 2.60

9.93 ± 1.36

10.59 ± 1.86

19.98 ± 2.49

( p < 0.02)

( p > 0.05)

( p > 0.05)

( p > 0.05)

( p > 0.05)

102.65 ± 1.56*

54.75 ± 2.77*

18.31 ± 1.84*

12.53 ± 1.79

14.41 ± 0.92

( p < 0.001)

( p < 0.05)

( p < 0.01)

( p > 0.05)

( p < 0.05)

81.97 ± 7.40

58.32 ± 5.70

16.45 ± 3.76

11.01 ± 1.97

14.22 ± 2.62

( p < 0.05)

( p > 0.05)

( p > 0.05)

( p > 0.05)

( p > 0.05)

83.40 ± 2.90

50.88 ± 1.54*

23.16 ± 1.40*

11.93 ± 0.96*

14.03 ± 1.10

( p > 0.05)

( p < 0.05)

( p < 0.05)

( p < 0.05)

( p > 0.05)

110.09 ± 5.33*

54.24 ± 1.50

15.52 ± 0.45*

21.53 ± 0.90*

8.71 ± 0.67*

( p < 0.001)

( p < 0.05)

( p < 0.001)

( p < 0.001)

( p < 0.001)

1 year, 4

2 years, 3

3 years, 3

Adults, 10

Note: Asterisks indicate statistically significant differences as compared with parameters of newborn animals; in parenthe sis—the degree of statistical significance of the differences as compared with the previous age (the same in Table 2).

individuals older than 6 years [3]. In the age groups of 1, 2, and 3 years, the animals kept from 1.5 month age in the aquacomplex of the Murmansk Marine Biological Institute (the Kola Bay) were examined. The combination of the freeliving and captive animals in one study was considered ac ceptable, based on the literature data confirming the practically identical biochemical blood com position in the abovementioned pinniped groups [4]. The blood was drawn from the extradural vein [5]. The plasma was separated by centrifugation. Total protein and its fractions, free amine nitro gen, urea, creatinine, glucose, total lipids, calci um, and inorganic phosphorus were determined in the plasma by using unified methods [6]. Modified albumin was revealed by the method of reprecipi tation in the trichloracetic acid—ethanol system proposed by Troitskii et al. [7]. Results of the work were processed statistically [8]. RESULTS AND DISCUSSION Study of the blood protein content and charac ter of distribution of its fractions serves as one of

the ways of evaluation of metabolic activities of tis sues and organs at the molecular level, as blood proteins are components of the dynamic circulat ing system reflecting physiologicalbiochemical peculiarities of the organism as a whole. The content of total protein as a rule increases with age [9, 10]. The protein concentration in adult seal is statistically significantly ( p < 0.001) higher than in their pups (110.09 ± 5.33 g/l vs 78.38 ± 2.59 g/l). The general regularity observed in various animal species is agespecific redistribution of pro teins by fractions [11, 12], the albumin level some what decreasing due to a decrease of use of protein for plastic processes as well as of intensity of albu min synthesis in liver. Meanwhile, the relative con centration of blood plasma globulins increases with age, which might be associated with a decrease of the rate of globulins decomposition in adult ani mals. As seen from data of Table 1, a rise of the total protein level in blood plasma of adult indi viduals occurs mainly at the expense of βglobulin fraction. Albumin in the blood plasma is submitted to conformational modifications in the process of performance of transport function; as a result, it is

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BIOCHEMICAL PARAMETERS OF BLOOD PLASMA OF THE HARP SEAL

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Table 2. Biochemical parameters of the blood plasma of the harp seals of different age Parameters

Age, the number of animals newborns, 19 1.5–2 months, 16

Free amino nitrogen (mmole/l)

4.24 ± 0.16

Urea (mmole/l)

15.59 ± 1.34

Creatinine (μmole/l)

154.79 ± 11.69

4.26 ± 0.16

15.73 ± 1.79

111.81 ± 6.39*

1 year, 4

2 years, 4

3 years, 4

adults, 10

2.56 ± 0.10*

1.36 ± 0.14*

3.01 ± 0.45*

3.15 ± 0.08*

( p < 0.001)

( p < 0.001)

( p < 0.02)

( p < 0.05)

10.03 ± 0.97*

17.72 ± 2.28

( p < 0.01)

( p < 0.02)

11.73 ± 0.57

Glucose (mmole/l)

2.23 ± 0.05

Total lipids (g/l)

11.72 ± 0.64

Total calcium (mmole/l)

6.12 ± 0.17

Inorganic phosphorus (mmole/l)

2.84 ± 0.12

25.38 ± 1.04*

3.76 ± 0.45*

15.58 ± 0.68*

7.94 ± 0.51*

3.73 ± 0.17*

( p > 0.05)

( p < 0.02)

291.11 ± 1.42* 194.69 ± 30.68 191.75 ± 33.48 117.83 ± 5.77* ( p < 0.001)

Modified al bumin (% of total albumin)

16.69 ± 0.95* 11.14 ± 1.61*

( p < 0.02)

( p > 0.05)

( p < 0.05)

24.82 ± 1.56* 27.10 ± 2.14* 28.46 ± 1.90* 31.37 ± 2.35* ( p > 0.05)

( p > 0.05)

( p > 0.05)

( p > 0.05)

6.92 ± 0.37*

7.74 ± 0.29*

5.90 ± 0.27*

2.78 ± 0.54

( p < 0.001)

( p > 0.05)

( p < 0.01)

( p < 0.001)

16.55 ± 0.53*

11.91 ± 0.83

10.37 ± 2.49

12.85 ± 0.55

( p > 0.05)

( p < 0.01)

( p > 0.05)

( p > 0.05)

6.28 ± 0.34

2.89 ± 0.28*

2.68 ± 0.1*

8.45 ± 0.70*

( p < 0.02)

( p < 0.001)

( p > 0.05)

( p < 0.001)

2.75 ± 0.09

1.62 ± 0.06*

1.50 ± 0.16*

3.89 ± 0.27*

( p < 0.001)

( p < 0.001)

( p > 0.05)

( p < 0.001)

represented in the blood circulation by a hetero geneous system of molecules. The modified albu min is combined concept, as this group includes molecules that have the common property: on treatment in the trichloracetic acid—ethanol sys tem, they lose the capability for dissolution in dis tilled water. Modifications of the protein structure are expressed in the form of the appearance of di verse conformers that as a rule are enriched in car bohydrates that are absent in the native fraction of this protein [13]. As seen from data of Table 2, the content of modified albumin (AM) is minimal in newborn individuals. After completion of milk nutrition (1.5–2 months) the seal pups start inde pendent feeding with invertebrates and fish. Qual itative changes in feeding also seem to affect the transport function of albumin, which is confirmed by a more than twofold elevation of the AM con centration in blood. The fact that subsequently the AM content practically does not change until the

adult state confirms the suggestion of the key role of nutrition (of composition of metabolites trans ported by albumin) in formation of a certain AM level. As seen from the data of Table 2, no statisti cally significant differences of this parameter be tween animals from the studied groups starting from the 1.5–2month age are revealed, although there is a tendency for an increase of the AM con tent in adult seals. It seems that the high AM con centration in adult animals is also determined by a decrease of the rate of catabolism of modified al bumin. Besides, a certain contribution to the rise of the AM level is also made by the strengthened the protein liganding under conditions of qualita tive and quantitative alterations of blood metabo lites with age. Apart from natural, physiological changes, the pathological ones, particularly infes tation with helminthes, also can be suggested. Hel minthic invasion increases intensively with transi tion of the seal pups to independent feeding; as a


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result, the sexually mature animals practically are 100%infected with helminthes, and the highest intensity of invasion is noted for the White Sea seals at the age of 13–16 years [14]. In the harp seal blood plasma, some metabolites— glucose, total lipids, free amine nitrogen, urea, cre atinine, total calcium, and inorganic phosphorus also were determined. Changes of these parameters with age are not uniform (Table 2). The blood plasma level of several parameters of nitrogen metabolism (free amine nitrogen, urea, creatinine) decreases with maturation of animals, which reflects the regular decrease of intensity of this component of metabolism. However, creati nine concentration in the blood plasma was found to be elevated at the age of 1–2 years as compared with that in newborn individuals and the 1.5–2 month old animals. The glucose content dynamics reflects the ap pearance of replacement of mechanisms of this main energy substrate in blood. The minimal con centration of glucose is revealed in newborn seals. This indicates that at once after the birth the ener gy source is the reserve of glucose delivered to the fetus by blood of the maternal body and the glu cose formed from lactate and free amino acids, but, as these reserves are spending, the main energy source is the fat of the maternal milk. The data of Table 2 demonstrate a rise of the glucose level in the blood of seals that have completed the milk feeding. This parameter is practically equal in the adults and pups, which is also found in other spe cies of pinnipeds [15]. It is obvious that the increase of the blood glucose content with aging results from gluconeogenesis, particularly from the free gluco genic amino acids. Besides, in the early ontogene sis of pinnipeds, the carbohydrate reserves of liver and of other tissues are actively used, which is in dicated by a high activity of glucose6phosphatase in animals from the adolescent group [15, 16]. The content of total lipids in the blood plasma increases substantially at the period of end of milk feeding and transition to independent feeding, then the level of this parameter decreases statistically significantly at the age of 2 years remains practi cally unchanged until the adult state. This agrees with the data on a significant reduction of the lipid content in blood of adult seals as compared with their pups [16]. Thus, our study allows us to speci

fy the age of formation of the steadily low level of lipids due to the possibility of studying the group of young seals (1–4 years). Of great interest is dynamics of parameters of mineral balance—the calcium and phosphorus content. By the end of the milk feeding their con centrations in the seal blood increases, although after the first year of life the calcium and phospho rus content is observed to decrease, the value of the ratio of these mineral substances also decreasing. At the age of 2 and 3 years this ratio is 1.78 and 1.74, respectively, whereas it is 2.15 in newborns and 2.17 in adult animals. The observed dynamics seems to reflect intensity of involvement of calci um and phosphorus in processes of formation of the bone tissue, as it is between the first and sec ond years of life that the seals have been noticed to increase the body length at the expense of their skeleton [17]. Thus, the obtained data characterize natural agerelated changes of several parameters of the metabolism of proteins, carbohydrates, lipids, and mineral substances in the harp seals, what is rec ommended to be considered at using the blood parameters for evaluation of effects of environmen tal factors on the organism. ACKNOWLEDGMENTS The work is supported by the Russian Founda tion for Basic Research (project no. 050448388). REFERENCES 1.

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