title: Trade-off between L-thyroxin and melatonin in immune regulation of the Indian palm squirrel, Funambulus pennanti during the reproductively inactive phase.
abstract: The thyroid gland and its hormones have been reported to influence reproduction and metabolism in a positive manner. However, research to date provides strong evidence for a reciprocal relationship between the immune system and hormones of the hypothalamus-pituitary-thyroid axis. The present study has been taken to elucidate the effect of L-thyroxin (T(4)) on immune parameters such as total leukocyte count, percent lymphocyte count, blastogenic response and percent stimulation ratio of thymocytes and splenocytes of a seasonally breeding rodent, Funambulus pennanti, during its reproductively inactive phase when peripheral T(4) is low. Treatment with L-thyroxin at a near-physiological dose of 35 microg/100 g body weight during evening hours showed a significant elevation of all immune parameters. However, combined treatment of L-thyroxin and melatonin (25 microg/100 g body weight) had no additive effect. On the other hand, in vitro supplementation of T(4) (10(-6) M) either alone or in combination with melatonin (0.5 microM) did not induce any significant change on thymocyte and splenocyte proliferation. Therefore, a trade-off effect of L-thyroxin and melatonin on the immune system (T- and B-cell differentiation) is suggested for this rodent.
authors.affiliation: Department of Zoology, Pineal Research Lab, Reproductive Biology Unit, Banaras Hindu University, Varanasi 221005, India.
authors.forename: Seema
authors.initials: S
authors.lastname: Rai
authors.forename: Chandana
authors.initials: C
authors.lastname: Haldar
authors.forename: Shiv Shankar
authors.initials: SS
authors.lastname: Singh
mesh_terms: D000818:Animals; D001853:Bone Marrow / Q000378:metabolism; D001854:Bone Marrow Cells / Q000378:metabolism; D002478:Cells, Cultured; D003470:Culture Media; D018655:Lymphocyte Count; D008214:Lymphocytes / Q000378:metabolism; D008297:Male; D008550:Melatonin / Q000097:blood / Q000502:physiology*; D012098:Reproduction / Q000502:physiology*; D012589:Sciuridae / Q000378:metabolism*; D013154:Spleen / Q000166:cytology; D013950:Thymus Gland / Q000166:cytology; D013974:Thyroxine / Q000097:blood / Q000502:physiology*
chemical_list: D003470:Culture Media; D008550:Melatonin; D013974:Thyroxine