TY - JOUR
T1 - Nighttime immunoreactive somatostatin content of the median eminence in hypo-and hyperthyroid rats
AU - Webb, S. M.
AU - Champney, T. H.
AU - Reiter, R. J.
N1 - Funding Information:
Acknowledgements-This study was supported by NSF grant No. PCM 800344 (RJR) and a grant from Innovative Research of America No. IRA-NG-83-13 (THC). At the time of the study, SMW was a recipient of a Fulbright Commission Grant.
PY - 1985
Y1 - 1985
N2 - 1. 1. The median eminence content of immunoreactive somatostatin (IRS) was measured by radioimmunoassay in 107 male albino rats, who were either hypothyroid after surgical thyroidectomy (N = 38), hyperthyroid following a subcutaneous implant of 5 mg of l-thyroxine (N = 36), or otherwise untreated (N = 33). 2. 2. Thyroid function was assessed by determining plasma levels of T4 and TSH from trunk blood obtained at the time of decapitation. Subgroups of animals from the 3 groups were killed either before (1800 hr), during (2200, 0200, 0400 hr), or after the dark portion of their 14:10LD photoperiod. 3. 3. Although no changes in median eminence IRS content were found throughout the period of study within any of the 3 groups, hypothyroid animals (297.23 ± 13.47 ng per ME; 620.41 ±58 ngIRS/mg protein) had a significantly lower median eminence IRS concentration than untreated rats (355.86 ± 16.55 ng of IRS per ME, P < 0.01; 906.86 ± 96.38 ng IRS/mg protein, P <0.05) and hyperthyroid animals (384.12 ± 14.67 ng per ME, P < 0.001; 874.1 ± 104.5 ng IRS//mg protein, P < 0.05). 4. 4. It is concluded, that the feedback of thyroid hormones on the hypothalamic-pituitary axis during thyroid hormone excess in vivo, contrary to what occurs in hypothyroidism, is probably independent of hypothalamic somatostatin.
AB - 1. 1. The median eminence content of immunoreactive somatostatin (IRS) was measured by radioimmunoassay in 107 male albino rats, who were either hypothyroid after surgical thyroidectomy (N = 38), hyperthyroid following a subcutaneous implant of 5 mg of l-thyroxine (N = 36), or otherwise untreated (N = 33). 2. 2. Thyroid function was assessed by determining plasma levels of T4 and TSH from trunk blood obtained at the time of decapitation. Subgroups of animals from the 3 groups were killed either before (1800 hr), during (2200, 0200, 0400 hr), or after the dark portion of their 14:10LD photoperiod. 3. 3. Although no changes in median eminence IRS content were found throughout the period of study within any of the 3 groups, hypothyroid animals (297.23 ± 13.47 ng per ME; 620.41 ±58 ngIRS/mg protein) had a significantly lower median eminence IRS concentration than untreated rats (355.86 ± 16.55 ng of IRS per ME, P < 0.01; 906.86 ± 96.38 ng IRS/mg protein, P <0.05) and hyperthyroid animals (384.12 ± 14.67 ng per ME, P < 0.001; 874.1 ± 104.5 ng IRS//mg protein, P < 0.05). 4. 4. It is concluded, that the feedback of thyroid hormones on the hypothalamic-pituitary axis during thyroid hormone excess in vivo, contrary to what occurs in hypothyroidism, is probably independent of hypothalamic somatostatin.
UR - http://www.scopus.com/inward/record.url?scp=0021904949&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0021904949&partnerID=8YFLogxK
U2 - 10.1016/0300-9629(85)90415-3
DO - 10.1016/0300-9629(85)90415-3
M3 - Article
C2 - 2859141
AN - SCOPUS:0021904949
SN - 0300-9629
VL - 80
SP - 575
EP - 577
JO - Comparative Biochemistry and Physiology -- Part A: Physiology
JF - Comparative Biochemistry and Physiology -- Part A: Physiology
IS - 4
ER -