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.
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.
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*
D000242:Cyclic AMP; D013974:Thyroxine