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Bursectomy and Its Influence on Circulating Corticosterone, Triiodothyronine, and Thyroxine in Immature Male Chickens1,2
Bursectomy and Its Influence on Circulating Corticosterone, Triiodothyronine, and Thyroxine in Immature Male Chickens1,2 MAGDI M. MASHALY Department of Poultry Science, The Pennsylvania State University, University Park, Pennsylvania 16802 (Received for publication May 25, 1983) ABSTRACT This investigation was carried out to determine the effect of bursectomy on circulating corticosterone, triiodothyronine (T3), and thyroxine (T4) in immature male chickens. One-day-old Single Comb White Leghorn male chicks were surgically bursectomized (BSX). Shamoperated chicks were used as control. Blood samples were collected from different BSX and sham birds at 2, 3, and 4 weeks of age. Serum concentrations of corticosterone, T3, and T4 were measured using radioimmunoassays. Serum concentrations of corticosterone and T3 were higher in BSX than sham-operated birds at all ages. Concentrations of T4, however, were similar in both groups. It was concluded that the bursa, directly or indirectly, affected hormone secretion from the thyroid and adrenal glands. (Key words: bursa of Fabricius, corticosterone, triiodothyronine, thyroxine, chickens) 1984 Poultry Science 63:798-800
INTRODUCTION The bursa of Fabricius is a lymphoid organ peculiar to avian species and its role in humoral immunity was discovered by Glick et al. (1956). The potential of an endocrine function of the bursa in relation to growth and sexual development was suggested as early as 1928 by Riddle. Subsequent investigations by Glick (1960a) revealed a negative correlation between the bursa and adrenal gland weights. Furthermore Glick and Dreesen (1967) found that chickens from a small bursa line had significantly larger adrenal glands than chickens from a large bursa line. The importance of the bursa of Fabricius as an endocrine gland became apparent when Brand et al, (1976) reported the presence of a bursal hormone (bursopoietin), which is responsible for B cell differentiation. Glick (1980) reviewed the role of the bursa of Fabricius as an endocrine gland. It is well established that hormones secreted from endocrine glands interact synergistically and antagonistically with each other in influencing different physiological systems in the body. To the best of our knowledge, there is no evidence on the influence of bursa of Fabricius on circulating hormones. Because the adrenals and
1
Supported in part by Biomedical Research Grant. Paper No. 6686 in the Journal Series of the Pennsylvania Agricultural Experiment Station. 2
thyroid are possible endocrine glands that could be under bursal influence (Glick, 1980), this investigation was carried out to determine the effect of bursectomy on circulating corticosterone, triiodothyronine (T 3 ), and thyroxine (T 4 ) in immature male chickens.
MATERIALS AND METHODS Experimental Animals. Single Comb White Leghorn male chicks were used in this study. The chicks were reared in batteries and maintained on food and water ad libitum. They received 14 hr of light and 10 hr of darkness (lights on 0800 to 2200 hr). Treatment and Hormone Measurements. One-day-old male chicks were surgically bursectomized (BSX) under local anesthesia (2% Lidocaine). Sham-operated birds were used as controls. Blood samples were collected from BSX and sham-operated birds at 2, 3, and 4 weeks of age. Different birds were bled at each age, so that each bird was bled only once. Furthermore, less than 1 min was required to remove the bird and obtain the blood sample. This minimized the elevation in corticosterone levels that accompany bird handling (Beuving and Vonder, 1978). Corticosterone, T 3 , and T 4 concentrations were measured in all serum samples using radioimmunoassays. Procedure for corticosterone assay was similar to that of Etches (1976) and was modified by Mashaly
798
BURSECTOMY EFFECTS ON IMMATURE MALES
et al. (1984). Assays of T 3 and T4 were similar to that of May (1978). Statistical Analysis. Student's t test was used to determine the significance of difference between BSX and sham-operated birds.
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RESULTS
Serum corticosterone concentrations in BSX and sham-operated birds are shown in Table 1. Mean corticosterone concentration was higher in BSX birds than in sham birds at all ages studied. The difference was significant at 2 (P<.1) and 4 weeks of age (P<.01), but not significant at 3 weeks of age. Concentrations of T 3 was also elevated in BSX birds (Table 1). The increase was significant at 3 (P<.02) and 4 (P<.01) weeks of age. The difference, however, was not significant at 2 weeks of age. There were no significant differences in serum T 4 concentrations between BSX and shamoperated birds at any of the ages (Table 1).
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The observed elevation of circulating T 3 in BSX birds was not anticipated because an in-
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Circulating corticosterone was elevated in bursectomized birds when compared with shams. However, Pedernera et al. (1980) found that corticosterone production by the adrenal gland in vitro was reduced in chick embryos surgically bursectomized by tail bud ablation. The difference in results may indicate that the influence of the bursa on endocrine functions depends on the stage of development of the bursa of Fabricius. Nevertheless, our result and the results by Pedernera et al. (1980) indicate that the bursa plays a role in controlling adrenal gland function. The importance of the bursa of Fabricius in adrenal ascorbic acid repletion of birds was reported by Freeman (1970). Furthermore, a negative correlation between the bursa and adrenal gland weights was previously reported (Glick, 1960a). That the bursa has an inhibitory effect on adrenal cortex output, as reflected by indirect evidence from the present study is not surprising, since adrenal cortical hormones (Glick, 1960b) are known to cause a regression of the bursa. Therefore, it is suggested that in order for the bursa to maintain its integrity, it secretes a hormone or humoral factor that suppresses circulating corticosterone. The level of this suppression, i.e., hypothalamus, pituitary, or adrenal, is yet to be determined.
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crease in T 3 concentration suggests a negative relationship exists between the bursa and thyroid gland. Such a relationship is inconsistent with the report by Snedecor (1971) in which he found that a reduction in bursa weight occurs in hypothyroid birds. Furthermore, thyroid hormones are known to enhance antibody production in mice (Chen, 1980). Thus, it is possible that the increase of circulating T3 in BSX birds is not a direct effect of the bursa but rather an indirect effect initiated by the rise of circulating corticosterone in BSX birds. In short, one explanation for our results could be the presence of a positive relationship between adrenal and thyroid glands, because both corticosterone and thyroid hormones have some physiological functions in common, i.e., both exert hyperglycemic effects. Greeman and Zarrow (1961) reported that corticosterone is one of the most active hyperglycemic steroids in chickens and thyroidectomy caused reduction in blood glucose levels in the duck (Ringer, 1976). Therefore, it could be concluded that bursa of Fabricius of immature male chickens, directly or indirectly, affects hormone secretion from adrenal and thyroid glands.
REFERENCES Beauving, G., and G.M.A. Vonder, 1978. Effect of stressing factors on corticosterone levels in plasma of laying hens. Gen. Comp. Endocrinol. 35:153-159. Brand, A., D. G. Gilmour, and G. Goldstein, 1976. Lymphocyte differentiating hormone of bursa of Fabricius. Science 193:319-321. Chen, Y., 1980. Effect of thyroxine on the immune response of mice in vivo and in vitro. Immunol. Commun. 9:269-276. Etches, R. J., 1976. A radioimmunoassay for corticosterone and its application to the measurement of stress in poultry. Steroids 28:763—773.
Freeman, B. M., 1970. The effect of adrenocorticot r o p i c hormone on adrenal weight and adrenal ascorbic acid in the normal and bursectomized fowl. Comp. Biochem. Physiol. 32:755-761. Glick, B., 1960a. Growth of the bursa of Fabricius and its relationship to die adrenal gland in White Pekin duck, White Leghorn, outbred and inbred New Hampshire. Poultry Sci. 39:130-139. Glick, B., 1960b. The effect of bovine growth hormone, desoxycorticosterone, and corticosterone on the weight of the bursa of Fabricius, adrenal glands, heart and body weight of young chickens. Poultry Sci. 39:1527-1533. Glick, B., 1980. The thymus and bursa of Fabricius: endocrine organs? Pages 209—229 in Avian Endocrinology. A. Epple and M. H. Stetson, ed. Academic Press, New York, NY. Glick, B., T. S. Chang, and R. G. Jaap, 1956. The bursa of Fabricius and antibody production. Poultry Sci. 35:224-225. Glick, B., and L. Dreesen, 1967. The influence of selecting for large and small bursa size on adrenal, spleen, and thymus weights. Poultry Sci. 46: 396-401. Greenman, D. L., and M. X. Zarrow, 1961. Steroids and carbohydrate metabolism in the domestic bird. Proc. Soc. Exp. Biol. Med. 106:459-462. Mashaly, M. M., M. L. Webb, S. L. Youtz, W. B. Roush, and H. B. Graves, 1984. Changes in serum corticosterone concentration of laying hens as a response to increased population density. Poultry Sci. 63:000-000. May, J. D., 1978. A radioimmunoassay for 3,5,3triiodothyronine in chicken serum. Poultry Sci. 57:1740-1745. Pedernera, E. A., M. Romano, J. P. Besedovsky, and M.D.C. Aquilar, 1980. The bursa of Fabricius is required for hormonal endocrine development in chicken. Gen. Comp. Endocrinol. 42:413—419. Riddle, O., 1928. Growth of the gonads and bursa of Fabricius in doves and pigeons with the data for body growth and age at maturity. Am. J. Physiol. 86:243-265. Ringer, R. K., 1976. Thyroids. Pages 359-371 in Avian Physiology. P. D. Sturkie, ed. 3rd ed. Springer-Verlag, New York, NY. Snedecor, J. G., 1971. Responses of normal and goitrogen-fed cockerels to different environmental temperatures. Poultry Sci. 50:237—243.
INTRODUCTION The bursa of Fabricius is a lymphoid organ peculiar to avian species and its role in humoral immunity was discovered by Glick et al. (1956). The potential of an endocrine function of the bursa in relation to growth and sexual development was suggested as early as 1928 by Riddle. Subsequent investigations by Glick (1960a) revealed a negative correlation between the bursa and adrenal gland weights. Furthermore Glick and Dreesen (1967) found that chickens from a small bursa line had significantly larger adrenal glands than chickens from a large bursa line. The importance of the bursa of Fabricius as an endocrine gland became apparent when Brand et al, (1976) reported the presence of a bursal hormone (bursopoietin), which is responsible for B cell differentiation. Glick (1980) reviewed the role of the bursa of Fabricius as an endocrine gland. It is well established that hormones secreted from endocrine glands interact synergistically and antagonistically with each other in influencing different physiological systems in the body. To the best of our knowledge, there is no evidence on the influence of bursa of Fabricius on circulating hormones. Because the adrenals and
1
Supported in part by Biomedical Research Grant. Paper No. 6686 in the Journal Series of the Pennsylvania Agricultural Experiment Station. 2
thyroid are possible endocrine glands that could be under bursal influence (Glick, 1980), this investigation was carried out to determine the effect of bursectomy on circulating corticosterone, triiodothyronine (T 3 ), and thyroxine (T 4 ) in immature male chickens.
MATERIALS AND METHODS Experimental Animals. Single Comb White Leghorn male chicks were used in this study. The chicks were reared in batteries and maintained on food and water ad libitum. They received 14 hr of light and 10 hr of darkness (lights on 0800 to 2200 hr). Treatment and Hormone Measurements. One-day-old male chicks were surgically bursectomized (BSX) under local anesthesia (2% Lidocaine). Sham-operated birds were used as controls. Blood samples were collected from BSX and sham-operated birds at 2, 3, and 4 weeks of age. Different birds were bled at each age, so that each bird was bled only once. Furthermore, less than 1 min was required to remove the bird and obtain the blood sample. This minimized the elevation in corticosterone levels that accompany bird handling (Beuving and Vonder, 1978). Corticosterone, T 3 , and T 4 concentrations were measured in all serum samples using radioimmunoassays. Procedure for corticosterone assay was similar to that of Etches (1976) and was modified by Mashaly
798
BURSECTOMY EFFECTS ON IMMATURE MALES
et al. (1984). Assays of T 3 and T4 were similar to that of May (1978). Statistical Analysis. Student's t test was used to determine the significance of difference between BSX and sham-operated birds.
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RESULTS
Serum corticosterone concentrations in BSX and sham-operated birds are shown in Table 1. Mean corticosterone concentration was higher in BSX birds than in sham birds at all ages studied. The difference was significant at 2 (P<.1) and 4 weeks of age (P<.01), but not significant at 3 weeks of age. Concentrations of T 3 was also elevated in BSX birds (Table 1). The increase was significant at 3 (P<.02) and 4 (P<.01) weeks of age. The difference, however, was not significant at 2 weeks of age. There were no significant differences in serum T 4 concentrations between BSX and shamoperated birds at any of the ages (Table 1).
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DISCUSSION
The observed elevation of circulating T 3 in BSX birds was not anticipated because an in-
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Circulating corticosterone was elevated in bursectomized birds when compared with shams. However, Pedernera et al. (1980) found that corticosterone production by the adrenal gland in vitro was reduced in chick embryos surgically bursectomized by tail bud ablation. The difference in results may indicate that the influence of the bursa on endocrine functions depends on the stage of development of the bursa of Fabricius. Nevertheless, our result and the results by Pedernera et al. (1980) indicate that the bursa plays a role in controlling adrenal gland function. The importance of the bursa of Fabricius in adrenal ascorbic acid repletion of birds was reported by Freeman (1970). Furthermore, a negative correlation between the bursa and adrenal gland weights was previously reported (Glick, 1960a). That the bursa has an inhibitory effect on adrenal cortex output, as reflected by indirect evidence from the present study is not surprising, since adrenal cortical hormones (Glick, 1960b) are known to cause a regression of the bursa. Therefore, it is suggested that in order for the bursa to maintain its integrity, it secretes a hormone or humoral factor that suppresses circulating corticosterone. The level of this suppression, i.e., hypothalamus, pituitary, or adrenal, is yet to be determined.
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crease in T 3 concentration suggests a negative relationship exists between the bursa and thyroid gland. Such a relationship is inconsistent with the report by Snedecor (1971) in which he found that a reduction in bursa weight occurs in hypothyroid birds. Furthermore, thyroid hormones are known to enhance antibody production in mice (Chen, 1980). Thus, it is possible that the increase of circulating T3 in BSX birds is not a direct effect of the bursa but rather an indirect effect initiated by the rise of circulating corticosterone in BSX birds. In short, one explanation for our results could be the presence of a positive relationship between adrenal and thyroid glands, because both corticosterone and thyroid hormones have some physiological functions in common, i.e., both exert hyperglycemic effects. Greeman and Zarrow (1961) reported that corticosterone is one of the most active hyperglycemic steroids in chickens and thyroidectomy caused reduction in blood glucose levels in the duck (Ringer, 1976). Therefore, it could be concluded that bursa of Fabricius of immature male chickens, directly or indirectly, affects hormone secretion from adrenal and thyroid glands.
REFERENCES Beauving, G., and G.M.A. Vonder, 1978. Effect of stressing factors on corticosterone levels in plasma of laying hens. Gen. Comp. Endocrinol. 35:153-159. Brand, A., D. G. Gilmour, and G. Goldstein, 1976. Lymphocyte differentiating hormone of bursa of Fabricius. Science 193:319-321. Chen, Y., 1980. Effect of thyroxine on the immune response of mice in vivo and in vitro. Immunol. Commun. 9:269-276. Etches, R. J., 1976. A radioimmunoassay for corticosterone and its application to the measurement of stress in poultry. Steroids 28:763—773.
Freeman, B. M., 1970. The effect of adrenocorticot r o p i c hormone on adrenal weight and adrenal ascorbic acid in the normal and bursectomized fowl. Comp. Biochem. Physiol. 32:755-761. Glick, B., 1960a. Growth of the bursa of Fabricius and its relationship to die adrenal gland in White Pekin duck, White Leghorn, outbred and inbred New Hampshire. Poultry Sci. 39:130-139. Glick, B., 1960b. The effect of bovine growth hormone, desoxycorticosterone, and corticosterone on the weight of the bursa of Fabricius, adrenal glands, heart and body weight of young chickens. Poultry Sci. 39:1527-1533. Glick, B., 1980. The thymus and bursa of Fabricius: endocrine organs? Pages 209—229 in Avian Endocrinology. A. Epple and M. H. Stetson, ed. Academic Press, New York, NY. Glick, B., T. S. Chang, and R. G. Jaap, 1956. The bursa of Fabricius and antibody production. Poultry Sci. 35:224-225. Glick, B., and L. Dreesen, 1967. The influence of selecting for large and small bursa size on adrenal, spleen, and thymus weights. Poultry Sci. 46: 396-401. Greenman, D. L., and M. X. Zarrow, 1961. Steroids and carbohydrate metabolism in the domestic bird. Proc. Soc. Exp. Biol. Med. 106:459-462. Mashaly, M. M., M. L. Webb, S. L. Youtz, W. B. Roush, and H. B. Graves, 1984. Changes in serum corticosterone concentration of laying hens as a response to increased population density. Poultry Sci. 63:000-000. May, J. D., 1978. A radioimmunoassay for 3,5,3triiodothyronine in chicken serum. Poultry Sci. 57:1740-1745. Pedernera, E. A., M. Romano, J. P. Besedovsky, and M.D.C. Aquilar, 1980. The bursa of Fabricius is required for hormonal endocrine development in chicken. Gen. Comp. Endocrinol. 42:413—419. Riddle, O., 1928. Growth of the gonads and bursa of Fabricius in doves and pigeons with the data for body growth and age at maturity. Am. J. Physiol. 86:243-265. Ringer, R. K., 1976. Thyroids. Pages 359-371 in Avian Physiology. P. D. Sturkie, ed. 3rd ed. Springer-Verlag, New York, NY. Snedecor, J. G., 1971. Responses of normal and goitrogen-fed cockerels to different environmental temperatures. Poultry Sci. 50:237—243.