Release of β-Endorphin by Prostaglandin E2 to Lower Plasma Glucose in Streptozotocin-Induced Diabetic Rats

J. T. Cheng; I. M. Liu; T. C. Chi; T. F. Tzeng

doi:10.1055/s-2001-16236

Hormone and Metabolic Research, Table of Contents

Horm Metab Res 2001; 33(7): 439-443
DOI: 10.1055/s-2001-16236

Original Clinical

Release of β-Endorphin by Prostaglandin E₂ to Lower Plasma Glucose in Streptozotocin-Induced Diabetic Rats

J. T. Cheng ¹ , I. M. Liu ¹ , T. C. Chi ¹ , T. F. Tzeng ²

¹ Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan City, Taiwan, R.O.C.
² Department of Internal Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung City, Taiwan, R.O.C.

Abstract

In the present study, Wistar rats, which received a streptozotocin injection to induce diabetes (STZ-diabetic rats), a model similar to insulin-dependent diabetes mellitus (IDDM) or type 1 diabetes mellitus, were used to investigate the effect of prostaglandin (PG) E₂ on plasma glucose. Intravenous injection of PGE₂ produced a dose-dependent lowering of plasma glucose level in fasting STZ-diabetic rats after 60 min. In addition to the blockade of this hypoglycemic effect by guanethidine (a noradrenergic nerve terminal-blocking agent), prazosin at a dose effective to block α₁-adrenoceptors abolished the action of PGE₂. An increase of plasma norepinephrine (NE) was also observed in STZ-diabetic rats receiving PGE₂ injections. Participation of sympathetic stimulation by PGE₂ may thus be speculated. Also, the plasma glucose-lowering effect of PGE₂ was also blocked by pretreatment with naloxone or naloxonazine at doses sufficient to block opioid µ-receptor. Injection of PGE₂ increased plasma β-endorphin-like immunoreactivity (BER) in STZ-diabetic rats, and this action was abolished by prazosin. Bilateral adrenalectomy resulted in the loss of this PGE₂ effect, and no increase was seen in plasma BER with PGE₂ in STZ-diabetic rats. Therefore, β-endorphin from the adrenal gland appears to be responsible for the lowering of plasma glucose in STZ-diabetic rats by PGE₂ through an increase of NE release to activate α₁-adrenoceptors.

Key words:

α₁-Adrenoceptor - β-Endorphin - PGE₂ - Diabetic Rats

Full Text

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Prof. Juei-Tang Cheng

Department of Pharmacology
College of Medicine
National Cheng Kung University

Tainan City
Taiwan 70101, R.O.C.

Phone: + 886-6-237-2706

Fax: + 886-6-238-6548

Email: jtcheng@mail.ncku.edu.tw