Thyroid hormone affects the hydrolysis of inositol phospholipids in the rat hypothalamus.
We have attempted to elucidate the effect of thyroid hormone on phospholipase C-linked inositol phospholipid hydrolysis in the rat hypothalamus. Hypothalamic slices of each animal, euthyroid control, hypothyroid, and thyroxine (T4)-supplemented hypothyroid rats were labeled with [3H]myoinositol in the presence of 5 mM LiCl, and then incubated for 60 min in KHG buffer containing either vehicle or 1 mM ouabain, a Na-K ATPase inhibitor. Hypothyroidism caused a significant increase in both basal and ouabain-stimulated accumulation of [3H]inositol phosphate ([3H]IP) in hypothalamic slices, whereas supplement with T4 to hypothyroid rats resulted in a complete restoration of hypothalamic [3H]IP formation to the value of euthyroid control. The present results indicate that thyroid hormone affects phospholipase C-linked inositol phospholipid hydrolysis in the hypothalamus, suggesting that negative feedback action of thyroid hormone may occur at a post-receptor site in the hypothalamus.
Iriuchijima
T
T
First Department of Internal Medicine, Gunma University School of Medicine, Maebashi, Japan.
Mizuma
H
H
Michimata
T
T
Ogiwara
T
T
Yamada
M
M
Murakami
M
M
Mori
M
M
D000818:Animals; D002712:Chlorides / Q000494:pharmacology; D006868:Hydrolysis; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007037:Hypothyroidism / Q000378:metabolism*; D066298:In Vitro Techniques; D007294:Inositol / Q000378:metabolism; D007295:Inositol Phosphates / Q000378:metabolism*; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology; D018021:Lithium Chloride; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D013961:Thyroid Gland / Q000502:physiology*; D013965:Thyroidectomy; D013974:Thyroxine / Q000494:pharmacology
D002712:Chlorides; D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D007294:Inositol; D010042:Ouabain; D008094:Lithium; D018021:Lithium Chloride; D013974:Thyroxine