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Stimulation of liver mitochondrial alpha-glycerophosphate dehydrogenase activity by L-thyroxine in thyroidectomized rats: comparison with the suppression of pituitary TSH secretion.
- Source :
-
Journal of endocrinological investigation [J Endocrinol Invest] 1990 Jan; Vol. 13 (1), pp. 61-4. - Publication Year :
- 1990
-
Abstract
- The rate of liver mitochondrial alpha-glycerophosphate dehydrogenase (GPD) induction was compared to the suppression of pituitary thyrotropin (TSH) secretion in thyroidectomized rats submitted to prolonged administration of small amounts of L-thyroxine (T4). With both 350 and 530 ng T4/100 g bw/day, liver alpha-GPD activity remained at post-thyroidectomy level (mean +/- SE: 0.030 +/- 0.002 and 0.034 +/- 0.001 delta A/mg prot/min, respectively) throughout all experiment. A sharp increase in enzyme activity was observed after 3 weeks of treatment in rats receiving 715 ng T4 / 100 g bw / day (mean +/- SE: 0.086 +/- 0.003 delta A/mg prot/min). In contrast, serum TSH levels were lower than pretreatment values (199 +/- 8ng/dI) in rats receiving 350 ng T4/100 g bw/day (mean +/- SE: 104 +/- 15 ng/dI; t = 7.48, p less than 0.001), decreased progressively with increasing T4 doses (m +/- SE:530 ng T4/100 g/day = 36 +/- 7 ng/dI); after only 48 h of treatment and were not significantly modified thereafter. The data are in agreement with the hypothesis of a nonlinear relationship between the degree of thyroid hormone receptor occupancy and the rate of liver mitochondrial alpha-GPD induction.
- Subjects :
- Analysis of Variance
Animals
Dose-Response Relationship, Drug
Enzyme Activation
Male
Mitochondria, Liver enzymology
Pituitary Gland metabolism
Radioimmunoassay
Rats
Rats, Inbred Strains
Thyroidectomy
Thyrotropin blood
Thyroxine blood
Glycerolphosphate Dehydrogenase metabolism
Mitochondria, Liver drug effects
Pituitary Gland drug effects
Thyrotropin metabolism
Thyroxine pharmacology
Subjects
Details
- Language :
- English
- ISSN :
- 0391-4097
- Volume :
- 13
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Journal of endocrinological investigation
- Publication Type :
- Academic Journal
- Accession number :
- 2319108
- Full Text :
- https://doi.org/10.1007/BF03348585