Adrenal tyrosine hydroxylase activation in the developing rat: influence of the thyroid status.
Adrenal tyrosine hydroxylase activation was elicited in developing control, hypo- and hyperthyroid rats by insulin-hypoglycaemia. Rats were deeply anaesthetized with chloroform at a low concentration, since intrinsic tyrosine hydroxylase activation was very low with this technique, as compared to Ketamine injection or chloroform at a high concentration. The study of time-course of tyrosine hydroxylase activation showed that the maximum value was observed 2 h after insulin administration. In control animals, tyrosine hydroxylase activation increased between 4 and 20 days, and then decreased. Hypothyroidism is associated with a decreased tyrosine hydroxylase activation between 4 and 50 days, as compared to controls and hyperthyroidism with an increased activation between 6 and 30 days. While tyrosine hydroxylase from saline-treated rats exhibits two different forms (with two apparent Km values for the cofactor), enzyme from insulin-treated animals was present in a single form with a Km corresponding to the low Km value of the saline-injected rats. At 6 and 14 days, hypothyroidism increases tyrosine hydroxylase Km values as compared to euthyroid animals.
Blouquit
M F
MF
Laboratoire d'Endocrinologie, Université Paris-Sud, Orsay, France.
Valens
M
M
Bagayoko
A
A
Gripois
D
D
D000311:Adrenal Glands / Q000196:embryology / Q000201:enzymology* / Q000254:growth & development; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D005314:Embryonic and Fetal Development; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006980:Hyperthyroidism / Q000139:chemically induced / Q000201:enzymology*; D007037:Hypothyroidism / Q000139:chemically induced / Q000201:enzymology*; D007328:Insulin / Q000494:pharmacology; D011247:Pregnancy; D011441:Propylthiouracil / Q000008:administration & dosage; D051381:Rats; D011919:Rats, Inbred Strains; D013974:Thyroxine / Q000008:administration & dosage; D014443:Tyrosine / Q000378:metabolism; D014446:Tyrosine 3-Monooxygenase / Q000187:drug effects*
D007328:Insulin; D014443:Tyrosine; D011441:Propylthiouracil; D014446:Tyrosine 3-Monooxygenase; D013974:Thyroxine