Receptor gene expression of glucagon-like peptide-1, but not glucose-dependent insulinotropic polypeptide, in rat nodose ganglion cells.
We previously reported that afferent signals of the rat hepatic vagus increased upon intraportal appearance of insulinotropic hormone glucagon-like peptide-1(7-36) amide (GLP-1), but not glucose-dependent insulinotropic polypeptide (GIP). To obtain molecular evidence for the vagal chemoreception of GLP-1, the concept derived from those electrophysiological observations, receptor gene expressions of GLP-1 and GIP in the rat nodose ganglion were examined by means of reverse transcriptase-mediated polymerase chain reaction (RT-PCR) and Northern blot analysis. Gene expression of the GLP-1 receptor was clearly detected by both RT-PCR and Northern blot analysis. In situ hybridization study confirmed that the expression occurs in neuronal cells of the ganglion. As to the GIP receptor, RT-PCR amplified the gene transcript faintly though Northern blot analysis failed to detect any messages. However, semi-quantitative RT-PCR revealed that the ratio of the gene expression level of the GIP receptor to that of the GLP-1 receptor was less than 1:250, indicating that receptor gene expression of GIP is practically negligible in the ganglion. Additionally, an equal level of GLP-1 receptor gene expressions between left- and right-side ganglia was evidenced by semi-quantitative RT-PCR, implying possible extrahepatic occurrence of vagal GLP-1 reception in addition to the reception through the hepatic vagus (originating from the left-side ganglion). The present results offer, for the first time, the molecular basis for the vagal chemoreception of GLP-1 via its specific receptor.
Nakagawa
Atsushi
A
Department of Internal Medicine, Kanazawa Medical University, Daigaku 1-1, Uchinada 920-0293, Japan. atch-n@kanazawa-med.ac.jp
Satake
Hanae
H
Nakabayashi
Hajime
H
Nishizawa
Makoto
M
Furuya
Keisuke
K
Nakano
Shigeru
S
Kigoshi
Toshikazu
T
Nakayama
Kohzo
K
Uchida
Kenzo
K
D000818:Animals; D001786:Blood Glucose / Q000235:genetics; D015152:Blotting, Northern; D002628:Chemoreceptor Cells / Q000378:metabolism; D007839:Functional Laterality / Q000235:genetics; D015870:Gene Expression / Q000235:genetics; D000067757:Glucagon-Like Peptide-1 Receptor; D017403:In Situ Hybridization; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D008099:Liver / Q000294:innervation / Q000502:physiology; D008297:Male; D009620:Nodose Ganglion / Q000166:cytology / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011964:Receptors, Gastrointestinal Hormone / Q000235:genetics*; D018027:Receptors, Glucagon / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017833:Visceral Afferents / Q000378:metabolism
D001786:Blood Glucose; C000593835:Glp1r protein, rat; D000067757:Glucagon-Like Peptide-1 Receptor; D007328:Insulin; D012333:RNA, Messenger; D011964:Receptors, Gastrointestinal Hormone; D018027:Receptors, Glucagon; C041086:gastric inhibitory polypeptide receptor