title: The effect of physiological doses of thyroxine on the level of cyclic adenosine-3',5'-monophosphate in pituitary and anterior hypothalamus of male rats of different age.
abstract: The levels of cAMP in the pituitary and anterior hypothalamus were determined by competitive binding to protein in male rats aged 2--2.5, 6--8 and 14--18 months. The lowest level of cAMP both in the pituitary and anterior hypothalamus (1.05 +/- 0.17 and 0.85 +/- 0.23 pM) (per mg wet weight, respectively) was found in 6--8 month-old rats. Administration of T4 (2 micrograms/100 g body weight, for 8 days) was followed by a decrease in cAMP level in the pituitary of 14--18 month-old animals, which was not the case with younger rats. The obtained results agree with the earlier observation that the threshold to homeostatic suppression in the hypothalamus-pituitary-thyroid system of rats decreases with aging. It is suggested that cAMP system contributes to the mechanism of changes in hypothalamic threshold and its pharmacological correction.
mesh_terms: D000375:Aging; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D008297:Male; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D051381:Rats; D013974:Thyroxine / Q000494:pharmacology*
chemical_list: D000242:Cyclic AMP; D013974:Thyroxine