ISSN 20790570, Advances in Gerontology, 2011, Vol. 1, No. 2, pp. 166–170. © Pleiades Publishing, Ltd., 2011. Original Russian Text © G.I. GubinaVakulik, L.A. Bondarenko, A.R. Gevorkyan, 2009, published in Uspekhi Gerontologii, 2009, Vol. 22, No. 4, pp. 626–630.

Morphological Response of the Pineal Gland of Old Animals to Melatonin Course Injection G. I. GubinaVakulika, L. A. Bondarenkob, A. R. Gevorkyanb a

Kharkiv National Medical University, pr. Lenina 4, Kharkiv, 61002 Ukraine Danilevsky Institute of Endocrine Pathology Problems, Ukrainian Academy of Medical Sciences, ul. Artema 10, Kharkiv, 61002 Ukraine email: [email protected]

b

Received February 12, 2009

Abstract—The effect of 10daylong evening melatonin injections in the physiological dose range on the mor phological state of the pineal gland was studied in old (18 to 20 months old) rat males of the Wistar population. It was shown with the use of nucleic acids histochemical staining that melatonin course injection into old rats caused dosedependant morphofunctional activation of pinealocytes that was accompanied by the increase in nuclei area, optical density of nuclei and cytoplasm. This fact was indicative of stimulation of epiphyseal hor mone production of both indole and polypeptidic nature. The use of melatonin in a dose of 0.05 mg/kg of body mass was accompanied by polyploidization of pinealocytes nuclei, and a dose of 0.50 mg/kg of body mass induced forced apoptosis. Keywords: pineal gland, melatonin, pinealocyte structure DOI: 10.1134/S207905701102007X

INTRODUCTION It is known that, with advancing age, the functional activity of the pineal gland decreases [2, 4, 13, 19, 21], and suppression of melatoninproducing function of the pineal gland takes place that causes hypomela toninemia [10, 23, 26, 27]. It is exerted morphologi cally in progressive decrease in general number of pinealocytes, increase in quantity of pigment and lipofuscincontaining cells, and progress of sclerosis features. The abovedescribed changes are character ized as agerelated hypopinealism. Taking into account that agerelated hypopineal ism afflicts all mammals, including human beings, and is characterized primarily by the progress of melatonin deficiency and the fact that melatonin possesses gero protective properties [22, 26, 28], melatonin prepara tions are often prescribed to elderly and senile people [9]. The majority of authors considers prescribing melatonin to be most reasonable in physiological doses that will provide an increase in the level of the hormone circulating in blood up to the value that is characteristic of healthy people of young reproductive age [3, 5, 12]. As white laboratory rats are used for the majority of preclinical drug trials, including hormonal ones, we have revealed physiological melatonin doses for this animal species in earlier experiments. They were from 0.05 to 0.50 mg/kg of body mass [9]. Despite the fact that melatonin preparations are being increasingly actively used in geriatric practice, the question of the effect of the injected hormone on the

structure and function of the pineal gland in the descending ontogenetic stage remains unclear today. On the basis of the foregoing, the purpose of the investigation was uncovering of special features of pinealgland histostructural changes in old rats after melatonin course injection. MATERIALS AND METHODS The work was performed using 15 old (18 to 20 month) male rats of the Wistar population that were kept in standard conditions in a vivarium. The investi gations were performed in winter (with a light regime of 8h light : 16h darkness). Melatonin (Sigma, United States) dissolved in physiological solution (with ethanol trace amounts) was introduced intrap eritoneally to the experimental animals in doses of 0.05 or 0.5 mg/kg of body weight daily at the end of the light phase 1 h before dark for 10 days. Control animals were injected with an analogous volume of the solvent. Rats were taken out from the experiment on the 11th day at midnight (the period of maximum activity of the pineal gland) under red light after sodium thio pental treatment according to the euthanasia condi tions noted in the guideline by Ukrainian Ministry of Healthcare [14]. Just after the extraction, brain epi physis was fixed in 10% formalin and saturated with paraffin. Micropreparations were stained by hematox ylin with eosin and gallocyanin by the Einarson method (summary nucleicacid staining). Analysis of

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Fig. 1. The structure of the pineal gland of an old rat (con trol group, night). The majority of pinealocytes have an angular shape with various degree of chromatin dispersity. Here and in Figs. 2 and 3, gallocyanin staining by the Ein arson method. 400× magnification.

Fig. 2. The structure of the pineal gland of an old rat after melatonin course injection in a dose of 0.05 mg/kg of body weight (night). Enlargement of pinealocyte nuclei and their nucleoli.

histological preparations was performed on an Axiostar microscope (Zeiss, Germany) supplied with a digital still camera. The description of microprepa rations was added by morphometric analysis per formed on computer images—karyometry, determi nation of nuclear and cytoplasmic optical density on micropreparations stained by gallocyanin which allows the DNA and RNA content to be determined [16]. The ploidy of pinealocytes’ nuclei was estimated with calculation of their relative quantities with poly ploid and hypodiploid nuclei [1]. Numeric material was statistically treated using Student’s ttest. RESULTS AND DISCUSSION It has been revealed that the pineal gland in old control animals at night has a morphofunctional pic ture indicative of active participation of its paren chyma in hormonal production, although the inten sity of the process is far less than in young mature ani mals. Pinealocytes have a small volume; it is difficult to identify cellular borders. The cytoplasm contains a great deal of RNA. The nuclei have an oval irregular shape and are dark. Heterochromatin is highly dis persed, and in the majority of large nuclei it is so highly dispersed that the nucleolus is well seen. Pinealocytes with euchromatic nuclei are rarely found. The described morphofunctional picture of the pineal gland is indicative of the preponderance of indoleam ines’ synthesis over polypeptides’ synthesis (Fig. 1). A number of apoptotic bodies are found under gallocya nin staining of sections, which shows the occurrence of physiological apoptosis of pinealocytes that is com mon for old animals. When using melatonin in a dose of 0.05 mg/kg of body weight, it is well seen that pinealocytes are more ADVANCES IN GERONTOLOGY

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compactly situated in comparison with the control group. Pinealocytes with an angular nucleus and highly vacuolated cytoplasm are found in the central part of the gland. It is evident that it is precisely these vacuoles that accumulate indoleamines. At the periphery of the pineal gland, the presence of pinealo cytes with a large euchromatic nucleus, displayed nucleolus, and eosinophilic cytoplasm, which is indic ative of polypeptides’ synthesis activation in them in comparison with old animals of the control group, is significant. Apoptosis intensity is far less than in the control group (Fig. 2). Morphometric investigation (table) has revealed an increase in the average area of the pinealocyte nucleus and in the optical density of nucleus and cytoplasm using summary nucleicacid staining, which, in com bination with the abovedescribed histological special features, can be considered as structural signs of both indoleamine and polypeptide synthesis activation. Ploidy determination of pinealocytic nuclei showed the increase in their relative quantity with polyploid nuclei. The increase in the dose of injected melatonin up to 0.5 mg/kg of body weight caused the appearance of even more marked activation of biosynthesis of biolog ically active compounds of both peptidic and indoleamine nature in pinealocytes (Fig. 3). An increase in the amount of apoptotic bodies was marked. Morphometric data (see table) reveal a fur ther increase in the average area of pinealocytic nuclei and the optical density of both nucleus and cyloplasm using summary nucleicacid staining. The determina tion of pinealocytic nuclei ploidy revealed an extended amount of pinealocytes with hypodiploid nuclei, which is indicative of their apoptotic state. The obtained results can be explained as follows. Exogenic melatonin injection before the night period

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Values of morphometric parameters of pinealocytes in old rats after melatonin course injection in various doses Group I Control, n1 = 5 II Melatonin 0.05 mg/kg, n1 = 5 III Melatonin 0.5 mg/kg, n1 = 5

Morphometric parameters Diploidy coeffi Statistical cient of pinealo parameters area of pinealo optical density of pi optical density of pine cytes nuclei cytes nuclei, µm2 nealocytes nuclei, cu alocytes cytoplasm, cu n2

120

20

120

120

x ± Sx

18.80 ± 0.49

0.088 ± 0.002

0.034 ± 0.003

2.01 ± 0.06

n2

160

160

160

160

x ± Sx

20.02 ± 0.38

0.118 ± 0.002

0.043 ± 0.002

2.88 ± 0.07

pIIIn

p < 0.05

p < 0.001

p < 0.05

p < 0.001

n2

280

280

280

280

x ± Sx

21.50 ± 0.39

0.126 ± 0.002

0.061 ± 0.002

2.26 ± 0.05

pIIIIn

p < 0.001

p < 0.001

p < 0.001

p < 0.01

pIIIIIn

p < 0.01

p < 0.001

p < 0.001

p < 0.001

Note: n1 is the animal quantity; n2 is the number of research targets in micropreparations.

for 10 days forms a low level of melatonin synthesizing function in the pineal gland with the organism that needs satisfaction by means of injected hormone usage. We have showed earlier that, after ten daily melatonin injections at a dose of 0.5 mg/kg of body weight, total saturation of melatonin receptors in the pineal gland takes place 30 min after the last injection; the process is accompanied by a decrease in cellular nuclei size and an increase in the quantity and size of transparent vacuoles in cytoplasm, this being consid ered as suppression of endogenic melatonin synthesis and excretion by exogenic melatonin [15]. In the present experiment, during a 10daylong course of melatonin injections, inhibition of endogenic melato

Fig. 3. The structure of the pineal gland of an old rat after a melatonin course injection in a dose of 0.5 mg/kg of body weight (night). Further enlargement of pinealocyte nuclei, increase in relative quantity of pinealocytes with highly dispersed chromatin in the nucleus.

nin production also occurred after every injection. However, taking out from the experiment was per formed more than a day after the last melatonin injec tion and both the histological picture of the pineal gland and the morphometric data are indicative of morphofunctional activation with signs of both indoleamine and polypeptide synthesis enhancement. The question arises as to the biosynthesis of which indoleamines is stimulated in pinealocytes of old rats under the action of melatonin course injection. It is impossible to definitely answer this question in this work, because further immunohistochemical investi gations are needed. Furthermore, taking into account that, in addition to melatonin, the pineal gland pro duces a whole family of oxy and methoxyindoles that are structurally similar but different in physio logical effects (serotonin, Nacetylserotonin, 5oxy and 5methoxytryptophan, 5oxy and 5methox ytryptophol, and 5oxy and 5methoxyindoleacetic acid), further investigation in this area should be promising. It is possible that exogenic melatonin injections stimulate the production of melatonin itself if exogenic melatonin turns out to be excreted from the organism during the time from the end of the course of melatonin injections until the animal’s death (more than a day). In this case hypermelatoninemia revealed in the same experiment may be caused by its hyperpro duction in the autologous pineal gland [8]. In any case, the results concerning an increase in the morphofunctional activity of pinealocytes of old rats during a course of melatonin injections in a phys iological dose are in accordance with the data of Semm, who noted an increase in the electrical activity of pinealocytes in rats after microphoretic melatonin injections directly into the pineal gland [24, 25]. The results of this series of investigations are of spe cial interest due to histologically revealed signs of ADVANCES IN GERONTOLOGY

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MORPHOLOGICAL RESPONSE OF THE PINEAL GLAND OF OLD ANIMALS

polypeptide synthesis stimulation because it is known that epiphyseal neuropeptides possess a pronounced geroprotective property [17, 18]. In this respect they are successfully used in geriatric practice as pharma ceuticals [11]. A very interesting special feature of the pineal gland’s response to exogenic melatonin injected in various doses was the revealed “dose–effect” phe nomenon toward pinealocytic apoptosis intensity depending on melatonin dose in the course of injec tions. It is well known that apoptosis (as programmed cell death) intensifies in ontogenesis with advancing age and helps the organism get rid of cells that have depleted their resources for living. It is also well known that apoptosis intensifies in the case of excess cell over work [6, 7, 20]. In our investigations the apoptotic process in pinealocytes of old rats of the control group is well pronounced, which confirms the present ideas on this question. A course of melatonin injection in the dose of 0.05 mg/kg of body weight significantly reduces pinealocytes’ apoptosis intensity with the enhancement of nuclei ploidy, while increasing the dose of the injected hormone up to 0.5 mg/kg of body weight intensifies apoptosis. Consequently, the results of the performed investi gation show that the pineal gland of old rats responds to course injection of exogenic melatonin with a change in morphofunctional characteristics, pointing at a dosedependent biosynthesis increase of com pounds of indole and peptidic nature. Moreover, while melatonin use in the dose of 0.05 mg/kg of body weight is mild for pinealocytes and stimulates nuclei ploidy, a dose of 0.5 mg/kg of body weight causes them to overwork and induces forced apoptosis. CONCLUSIONS Melatonin course injection into old rats causes the appearance of histological signs of dosedependent activation of the pineal gland. Dosedependent increase in the area and optical density of pinealocyte nuclei with simultaneous increase in the optical density of cytoplasm when stained for summary nucleic acids after course mela tonin injection confirms the presence of production stimulation of compounds of both indole and peptidic nature in the pineal gland. Melatonin use in a dose of 0.05 mg/kg of body weight is mild for pinealocytes of old rats, inhibits apo ptotic processes in these cells, and is accompanied by polyploidization, while melatonin use in a dose of 0.5 mg/kg of body weight causes them to overwork and induces forced apoptosis. It can be proposed that the geroprotective effect of evening melatonin injection intensifies due to simulta neous stimulation of neuropeptide biosynthesis in the pineal gland. ADVANCES IN GERONTOLOGY

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REFERENCES 1. Avtandilov, G.G. and Saniev, K.B., Ploidometry in Improving the Quality of Pathohistologic Diagnosis, Arkh. Patol., 2002, vol. 64, no. 3, pp. 31–33. 2. Anisimov, V.N., Molekulyarnye i fiziologicheskie mekh anizmy stareniya (Molecular and Physiological Mecha nisms of Aging), St. Petersburg: Nauka, 2003. 3. Anisimov, V.N., The Effect of Melatonin on Aging Pro cess, in Melatonin v norme i patologii (Melatonin in Nor mal State and Pathologic Conditions), Komarov, F.I., Ed., Moscow: Medpraktika, 2004, pp. 223–237. 4. Anisimov, V.N., AgeRelated Changes of Epiphyseal Function, in Melatonin v norme i patologii (Melatonin in Normal State and Pathologic Conditions), Komarov, F.I., Ed., Moscow: Medpraktika, 2004, pp. 20–33. 5. Arushanyan, E.B., Unikalnyi melatonin (biologicheskie svoistva i farmakologiya) (Unique Melatonin (Biological Properties and Pharmacology), Stavropol’: StGMA, 2006. 6. Belushkina, N.N. and Severin, S.E., Molecular Mech anisms of Apoptosis Pathology, Arkh. Patol., 2001, vol. 63, no. 1, pp. 51–60. 7. Zhizhina, G.P., The Role of Apoptosis in Normal Ontogenesis, Pathogenesis and Aging, Klin. Geront., 2002, vol. 8, no. 4, pp. 3–10. 8. Bondarenko, L.A., Gorbach, T.V., and Gevorkyan, A.R., Determination of Exogenic Melatonin Dose Regenerat ing the Concentration of the Hormone Circulating in Blood of Old Rats with AgeRelated Hypopinealism, Probl. Endocrinol. Path., 2008, no. 3, pp. 56–61. 9. Kvetnaya, T.V. and Knyaz’kin, I.V., Melatonin: rol' i znachenie v vozrastnoi patologii (Melatonin: Role and Relevance in AgeRelated Pathology), St. Petersburg: VMedA, 2003. 10. Korkushko, O.V., Khavinson, V.Kh., Shatilo, V.B., et al., Circadian Rhythms of Pineal Gland MelatoninForm ing Function in Elderly People, Adv. Gerontol., 2004, no. 15, pp. 70–75. 11. Korkushko, O.V., Khavinson, V.Kh., Shatilo, V.B., et al., Effect of Peptide Preparation Epithalamin on Circadian Rhythm of Epiphyseal MelatoninProduc ing Function in Elderly People, BEBM, 2004, vol. 137, no. 4, pp. 441–443. 12. Korkushko, O.V., Shatilo, V.B., and Khavinson, V.Kh., Pineal’naya zheleza: puti korrektsii pri starenii (Pineal gland: Ways of Correction in Aging), St. Petersburg: Nauka, 2006. 13. Novikova, I.A., Kovalenko, R.I., and Nozdrachev, A.D., Characteristics of Structural and Functional Organization of the Rat Pineal Gland Depending on Age, Dokl. Akad. Nauk, 1997, vol. 355, no. 6, pp. 834–837. 14. Reznikov, O.G., General Principals of Experiments on Animals, Endokrynologia, 2003, vol. 8, no. 1, pp.142– 145. 15. RomBugoslavskaya, E.S., Bondarenko, L.A., and GubinaVakulik, G.I., Mekhanizmy autokrinnoi regu lyatsii funktsii epifiza, Neirofiziologiya, 1998, vol. 30, no. 3, pp. 163–170. 16. Tashke, K., Vvedenie V Kolichestvennuyu Tsitogistolog icheskuyu Morfologiyu. Bukharest: Izd. Akad. Sots. Respubliki Rumynii, 1980.

170

GUBINAVAKULIK et al.

17. Khavinson, V.Kh. and Morozov, V.G., Geroprotektor naya effektivnost’ timalina i epitalamina, Adv. Geron tol., 2002, vol. 10, pp. 74–84. 18. Khavinson, V.Kh. and Anisimov, V.N., Peptidnye bio regulyatory i starenie (Peptide Bioregulators and Aging), St. Petersburg: Nauka, 2003. 19. Khmel’nitskii, O.K. and Stupina, A.S., Funkt sional’naya morfologiya endokrinnoi sistemy pri aterosk leroze i starenii (Functional Morphology of Endocrine System in Atherosclerosis and Aging), Moscow: Med itsina, 1989. 20. Shvemberger, I.N. and Ginkul, L.B., Apoptosis: Role in Normal Ontogenesis and in Pathologic Conditions, Vopr. Onkol., 2002, vol. 48, no. 2, pp. 153–158. 21. Karazek, M., Melatonin, Human Aging, and Age Related Diseases, Exp. Geront., 2004, vol. 39, nos. 11–12, pp. 1723–1729. 22. Reiter, R.J., Melatonin: Clinical Relevance, Best Pract. Res. Clin. Endocr. Metab., 2003, vol. 17, no. 2, pp. 273– 285.

23. Ruzsas, C. and Mess, B., Melatonin and Aging. A Brief Survey, Neuroendocrinology Lett., 2000, vol. 21, no. 1, pp. 17–23. 24. Semm, P., Electrophysiology of the Mammalian Pineal Gland: Evidence for Rhythmical and Nonrhythmical Elements and for Magnetic Influence on Electrical Activity, in Structure and Function of the Vertebrate Circa dian System, Asehoff, J., Ed., Berlin, 1982, pp. 35–52. 25. Semm, P., Neurobiological Investigations of the Pineal Gland and Its Hormone Melatonin, in Pineal Gland and Endocrine Role, Axelrod, J., Fraschini, F., and Velo, G.P., Eds., New York: Plenum Press, 1983, pp. 437–465. 26. Touitou, Y., Human Aging and Melatonin. Clinical Relevance, Exp. Geront., 2001, vol. 36, no. 7, pp. 1083– 1100. 27. Waldhauser, F., Kovacs, J., and Reiter, E., AgeRelated Changes in Melatonin Levels in Humans and Its Poten tial Consequences for Sleep Disorders, Exp. Geront., 1998, vol. 33, nos. 7–8, pp. 759–772. 28. Wetterberg, L., Melatonin and Clinical Application, Reprod. Nutr. Dev., 1999, vol. 39, no. 3, pp. 367–382.

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