Insulin-Like Material in Parotid and Submaxillary Salivary Glands of Normal and Diabetic Adult Male Mice

Acid-ethanol extracts of homogenates from the parotid and submaxillary salivary glands of normal and strep-tozocin-induced diabetic adult male mice were investigated for insulin-like material. Extracts of both the parotid and submaxillary glands contained insulin-like immunoreactivity. The values were 156 ± 72 ng/g wet tissue in the parotid and 104 ± 36 ng/g wet tissue in the submaxillary gland. Fractionation of this material on Sephadex G-50 (superfine) columns revealed a single peak conresponding to the elution volume of isotopically labeled insulin. Isolated fat cells were stimulated by these extracts to convert [¹⁴C]glucose to ¹⁴CO₂. This effect was blocked by preincubation with anti-insulin serum. It was observed with the avidin-biotin immunocytochemical technique that both the parotid and submaxillary glands of adult male mice possess a population of cells containing an insulin-like material. After intraperitoneal injection of streptozocin there was a marked decrease of insulin-like material extractable from both the parotid and submaxillary glands. However, this β-cell cytotoxic agent did not completely destroy the salivary cells containing the insulin-like material. These data suggest that both the parotid and submaxillary salivary glands may be extrapancreatic sources of insulin in mice.