TY - JOUR
T1 - Immune-neuroendocrine interactions during aging
T2 - Age-dependent thyrotropin-inhibiting activity of thymosin peptides
AU - Goya, Rodolfo G.
AU - Takahashi, Sumio
AU - Quigley, Kathleen L.
AU - Sosa, Yolanda E.
AU - Goldstein, Allan L.
AU - Meites, Joseph
N1 - Funding Information:
Thymosin fraction 5 (TF-5), a partially purified thymic preparation, has been previously shown to have luteinizing hormone-releasing hormone (LH-RH)-releasing activity in perfused rat hypothalamus as well as in vivo stimulatory effect on the pituitary-adrenal axis in prepubertal monkeys. We report here the effect of TF-5 on the TSH-thyroid axis in young (3 months) and old (25 months) Sprague-Dawley male rats. Conscious free-moving animals carrying an indwelling atrial cannula received a single dose of 5 mg/kg body wt. of either bovine serum albumin (BSA) or TF-5 via the cannula. In the young rats, TF-5 induced a marked reduction of plasma thyrotropin (TSH) which was significantly greater than the normal circadian decline observed in the BSA-treated controls. The old males displayed high basal levels of TSH which showed no circadian rhythmicity, and did not respond to TF-5. Thyroxine (T4), triiodothyronine (T3), corticosterone, and prolactin levels were not affected by TF-5 at the dose levels tested. The old rats had significantly lower basal levels of T4, but not T 3, than their young counterparts. The synthetic peptides thymosin ~-1 and serum thymic factor, which are components of TF-5, had no effect on the above hormones when injected in doses up to 5/~g/kg body wt. Acute thymectomy in 3-month-old males induced a significant increase in basal levels of TSH without affecting plasma T4 or T 3. These results suggest that the thymus has an inhibitory *This work was aided in part by NIH grant AG00416 to J. Meites and a grant from the Biotechnology Research Center, Michigan State University, to R. Goya. tPresent address: Zoological Institute, Faculty of Science, Hiroshima University, Naka-ku, Hiroshima 730, Japan. Address all correspondence to: Joseph Meites, Department of Physiology,M ichigan State University, East Lansing, MI 48824-1101, U.S.A.
PY - 1987/12
Y1 - 1987/12
N2 - Thymosin fraction 5 (TF-5), a partially purified thymic preparation, has been previously shown to have luteinizing hormone-releasing hormone (LH-RH)-releasing activity in perfused rat hypothalamus as well as in vivo stimulatory effect on the pituitary-adrenal axis in prepubertal monkeys. We report here the effect of TF-5 on the TSH-thyroid axis in young (3 months) and old (25 months) Sprague-Dawley male rats. Conscious free-moving animals carrying an indwelling atrial cannula received a single dose of 5 mg/kg body wt. of either bovine serum albumin (BSA) or TF-5 via the cannula. In the young rats, TF-5 induced a marked reduction of plasma thyrotropin (TSH) which was significantly greater than the normal circadian decline observed in the BSA-treated controls. The old males displayed high basal levels of TSH which showed no circadian rhythmicity, and did not respond to TF-5. Thyroxine (T4), triiodothyronine (T3), corticosterone, and prolactin levels were not affected by TF-5 at the dose levels tested. The old rats had significantly lower basal levels of T4, but not T3, than their young counterparts. The synthetic peptides thymosin α-1 and serum thymic factor, which are components of TF-5, had no effect on the above hormones when injected in doses up to 5 μg/kg body wt. Acute thymectomy in 3-month-old males induced a significant increase in basal levels of TSH without affecting plasma T4 or T3. These results suggest that the thymus has an inhibitory action on TSH in the rat, which is not mediated by the thyroid gland. Our results also suggest an age-related desensitization of the TSH system to thymic influence in this species.
AB - Thymosin fraction 5 (TF-5), a partially purified thymic preparation, has been previously shown to have luteinizing hormone-releasing hormone (LH-RH)-releasing activity in perfused rat hypothalamus as well as in vivo stimulatory effect on the pituitary-adrenal axis in prepubertal monkeys. We report here the effect of TF-5 on the TSH-thyroid axis in young (3 months) and old (25 months) Sprague-Dawley male rats. Conscious free-moving animals carrying an indwelling atrial cannula received a single dose of 5 mg/kg body wt. of either bovine serum albumin (BSA) or TF-5 via the cannula. In the young rats, TF-5 induced a marked reduction of plasma thyrotropin (TSH) which was significantly greater than the normal circadian decline observed in the BSA-treated controls. The old males displayed high basal levels of TSH which showed no circadian rhythmicity, and did not respond to TF-5. Thyroxine (T4), triiodothyronine (T3), corticosterone, and prolactin levels were not affected by TF-5 at the dose levels tested. The old rats had significantly lower basal levels of T4, but not T3, than their young counterparts. The synthetic peptides thymosin α-1 and serum thymic factor, which are components of TF-5, had no effect on the above hormones when injected in doses up to 5 μg/kg body wt. Acute thymectomy in 3-month-old males induced a significant increase in basal levels of TSH without affecting plasma T4 or T3. These results suggest that the thymus has an inhibitory action on TSH in the rat, which is not mediated by the thyroid gland. Our results also suggest an age-related desensitization of the TSH system to thymic influence in this species.
KW - Age-related response
KW - Aging
KW - TSH inhibition
KW - Thymus
KW - Thyrotropin
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U2 - 10.1016/0047-6374(87)90042-X
DO - 10.1016/0047-6374(87)90042-X
M3 - Article
C2 - 3431174
AN - SCOPUS:0023605355
SN - 0047-6374
VL - 41
SP - 219
EP - 227
JO - Mechanisms of Ageing and Development
JF - Mechanisms of Ageing and Development
IS - 3
ER -