The effects of cysteamine on thyrotropin and immunoreactive beta-endorphin secretion in the rat
We examined the effects of the thiol agent cysteamine (CSH), which is known to deplete the hypothalamus of immunoreactive somatostatin, on physiological TSH and beta- endorphin secretion in the adult male rat. CSH at doses of 90 and 300 mg/kg CSH produced a rapid decline in plasma TSH, whereas a dose of 30 mg/kg did not alter plasma TSH levels. After the higher doses of CSH, TSH levels in the blood remained lower than control values on day 2, but returned to normal by 1 week. This decrease in TSH within the plasma was not associated with a reduction in hypothalamic TRH concentrations. The TSH response to 500 ng/kg TRH was normal in CSH-treated animals. Blockade of norepinephrine synthesis with diethyldithiocarbamate (500 mg/kg) or fusaric acid (100 mg/kg) inhibited TSH secretion in a manner similar to that of CSH. beta-Endorphin-like immunoreactivity (bet-End-LI) was elevated in the plasma immediately after CSH (300 mg/kg) administration. This was associated with a 58% reduction in anterior pituitary beta-End-LI and no change in hypothalmic beta-End-LI. Plasma beta-End-LI returned to normal on day 2. The increase in plasma beta-End-LI induced by immobilization stress was not compromised by CSH treatment. The observed effects of CSH on both TSH and beta-End-LI are consistent with a reduction in central norepinephrine neurotransmission through the known actin of CSH to inhibit dopamine-beta-hydroxylase. Acute stress may play a role as well in the observed changes in TSH and beta-End-LI secretion.
- Research Organization:
- Department of Neurology, Massachusetts General Hospital, Boston
- OSTI ID:
- 6250263
- Journal Information:
- Endocrinology; (United States), Vol. 112:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ENDORPHINS
SECRETION
HYPOTHALAMUS
INHIBITION
MEA
BIOLOGICAL EFFECTS
TOXICITY
TRH
BIOCHEMISTRY
BIOELECTRICITY
BIOLOGICAL PATHWAYS
BLOOD PLASMA
DOSE-RESPONSE RELATIONSHIPS
ENZYME ACTIVITY
SOMATOSTATIN
TSH
AMINES
AUTONOMIC NERVOUS SYSTEM AGENTS
BIOLOGICAL MATERIALS
BLOOD
BODY
BODY FLUIDS
BRAIN
CENTRAL NERVOUS SYSTEM
CHEMISTRY
DRUGS
ELECTRICITY
HORMONES
MATERIALS
NERVOUS SYSTEM
NEUROREGULATORS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANS
PEPTIDE HORMONES
PITUITARY HORMONES
RADIOPROTECTIVE SUBSTANCES
THIOLS
560306* - Chemicals Metabolism & Toxicology- Man- (-1987)