TISSUE DISTRIBUTION OF RAT GLUCAGON RECEPTOR AND GLP-1 RECEPTOR GENE-EXPRESSION

The regulation of glucose metabolism by glucagon and GLP-1 is well est ablished, but novel functions for these and other proglucagon-derived peptides are less well defined. This paper highlights the diversity of both GLP-1 and glucagon activity by studying the tissue distribution of glucagon and GLP-1 receptor gene expression by both Southern blot a nalysis of RT-PCR products and nuclease protection assays. By Southern blot analysis of RT-PCR products, GLP-1 receptor mRNA was detected in lung, hypothalamus, hippocampus, cerebral cortex, kidney, pancreas, a nd throughout the gastrointestinal tract. Glucagon receptor expression was detected in liver, kidney, spleen, thymus, adrenal glands, pancre as, cerebral cortex, lung, and throughout the gastrointestinal tract. Nuclease protection assay revealed glucagon receptor expression to be highest in liver and kidney, whereas GLP-1 receptor expression was onl y detected by protection assay in lung, stomach, and large bowel. Desp ite previous evidence that other receptors for proglucagon-derived pep tides may exist, no evidence of novel receptors or multiple isoforms o f the glucagon and GLP-1 receptors was found, indicating that the two cloned receptors may mediate all the effects of proglucagon-derived pe ptides, or that novel receptors may share less homology with the gluca gon and GLP-1 receptors than previously anticipated. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.