Immunoreactive Glucagon in the Salivary Glands of Man and Animal
Recent observations that immunoreactive glucagon levels rise following pancreatectomy and even after total evisceration suggested that extra-pancreatic sources of glucagon other than the gastrointestinal tract probably did exist. Acid-saline extractions of many tissues failed to reveal glucagon-like material except in the salivary glands of rats, mice, rabbits, dogs, and man. This material appeared to be in greatest quantity in the submaxillary glands of rodents. Sephadex column fractionation and gel electrophoresis indicate that this material has a molecular weight of approximately 70,000. Refractionation or treatment with urea and acetic acid failed to alter the chromatographic pattern of this material. Injection of rat submaxillary gland glucagon-like immunoreactive material produced hyperglycemia equivalent to that obtained with immunoequivalent amounts of pure porcine pancreatic glucagon. Low glucose concentrations stimulated and high glucose concentrations suppressed the release of this material into tissue culture medium and arginine was a potent stimulus to the release of salivary gland glucagon. Despite a chromatographic profile quite different from that of native pancreatic glucagon, this material cross-reacted identically with the 30K glucagon antiserum thought to be specific for A cell glucagon. Electron microscopy of the submaxillary glands revealed marked accumulation of electron dense secretory granules in the basilar portion of ductular cells and occasional acinus cells with similar appearing granules.
KeywordsSugar Albumin Urea Carbohydrate Glycine
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