Summary
Fasting plasma GLP-1 levels were significantly higher in hypophysectomized (hypox)
rats (n = 6) than in intact (normal) rats (n = 7) (54.3 ± 5.2 vs. 33.3 ± 2.4 pmol/L, p < 0.001). To examine the influence of pituitary hormones on
plasma GLP-1 levels, concentrations of plasma glucose, insulin and GLP-1 after an
oral glucose load to hypox rats that were given either rat growth hormone (rGH) (n
= 7), cortisol and thyroxine (n = 7) or no substitution (n = 6) were compared with
those of normal rats (n = 7). Plasma glucose levels in the fasting state and after
the glucose ingestion were significantly lower in hypox rats, but the hormonal replacements
to hypox rats increased their total glucose levels to those of normal rats, although
the increasing patterns were different from those in normal rats. Insulin levels both
in the fasting state and after the glucose ingestion were significantly decreased
in hypox rats and the fasting and total GLP-1 levels were significantly increased
in those rats. rGH substitution significantly increased the total insulin levels in
hypox rats and decreased the fasting and total GLP-1 levels closely to levels in normal
rats, while substitution with cortisol and thyroxine failed to introduce such a significant
effect. These results suggested that secretion of GLP-1 might be influenced by the
function of GH.
Key words:
Hypophysectomized rat - plasma GLP-1 - GH - oral glucose tolerance test
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Ph.D. Kayoko Tateishi
Department of Biochemistry
Fukuoka University School of Medicine
45-1, 7-chome Nanakuma, Jonan-ku
Fukuoka 814-0180
Japan
Phone: + 81-92-801-1011
Fax: + 81-92-801-3600
Email: tateishi@fukuoka-u.ac.jp
