AJP - Endocrinology and Metabolism, Vol 238, Issue 3 258-E266, Copyright © 1980 by American Physiological Society
Tissue distribution of glucagon, glucagonlike immunoreactivity, and insulin in the rat
A. Perez-Castillo and E. Blazquez
To show that glucagon, glucagonlike immunoreactivity (GLI), and insulin are
synthetized by organs other than the pancreas and the gastrointestinal
tract, different rat tissue acid-ethanol extracts were obtained and
analyzed by immunoassay using specific antisera. Significant amounts of
glucagon were found in the gastrointestinal tract (44.77 +/- 5.4 ng),
salivary glands (1.50 +/- 0.17 ng), thymus (2.80 +/- 0.46 ng), thyroid
(0.25 +/- 0.02 ng), and adrenal glands (0.25 +/- 0.06 ng). Whereas GLI
appeared in the gut mucosa, adrenal and salivary glands, genuine insulin
was detected only in the pancreas. Aliquots of the tissue extracts,
fractionated on Bio Gel P 30 columns, gave a 3,500 mol wt immunoreactive
(30 K) peak that behaved as pancreatic glucagon on acrylamide gel
electrophoresis and displaced 125I-labeled glucagon previously bound to its
hepatic receptors. Arginine, epinephrine, and low glucose concentrations
stimulated glucagon release from parotid, thymus, and thyroid. Active
glucagon biosynthesis by these organs was established by the incorporation
of L-[3H]tryptophan into a 3,500 mol wt polypeptide with specific immune
reaction with 30 K antiserum. These results suggest that different rat
tissues can contribute to the circulating levels of glucagon and GLI and
therefore to metabolic homeostasis.
