Glucose affects the release of thyrotropin-releasing hormone from the rat hypothalamus.
We have attempted to elucidate the effect of glucose concentrations on the release of thyrotropin-releasing hormone (TRH), a brain neuropeptide possessing glucoregulatory function, from rat hypothalamic slices in vitro. Rat hypothalamic slices were preincubated for 60 min at 37 degrees C in Krebs-Ringer bicarbonate (KRB) buffer (pH 7.4) containing varying concentrations of glucose (10, 5, 2.5 and 1 mM), and then tissues were incubated in KRB buffer, followed by stimulation with 60 mM K+ or 1 mM ouabain. In addition, after inducing hypoglycemia by insulin administration in the rat, hypothalamic tissues were dissected out and preincubated in KRB buffer (10 mM glucose) and then incubated in fresh KRB buffer containing 1 mM ouabain. A decrease in the glucose concentration of incubation medium caused a dose-dependent decrease in both K(+)- and ouabain-stimulated TRH release from rat hypothalamic slices. Furthermore, the ouabain-stimulated TRH release from the hypothalamus of rats with insulin-induced hypoglycemia was significantly reduced (45% of control values; p less than 0.01). The present results indicate that in vitro and in vivo hypoglycemia resulted in a significant decrease in the release of TRH from the hypothalamus, suggesting that circulating glucose levels affect TRH release which, in turn, might be responsible for peripheral glucoregulation.
Yamaguchi
M
M
1st Department of Internal Medicine, Gunma University School of Medicine, Maebashi, Japan.
Iriuchijima
T
T
Michimata
T
T
Mori
M
M
D000818:Animals; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology*; D007003:Hypoglycemia / Q000139:chemically induced / Q000378:metabolism; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007328:Insulin; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism*
D007328:Insulin; D010042:Ouabain; D013973:Thyrotropin-Releasing Hormone; D005947:Glucose; D011188:Potassium