Increases in concentrations of somatostatin- and insulin-like immunoreactivities in submandibular salivary gland of diabetic rats: effect of insulin treatment

Abstract

Abstract. To investigate whether systemic insulin levels can influence somatostatin-like immunoreactivity and insulin-like immunoreactivity concentrations in the rat submandibular salivary glands, we measured the concentrations of the two peptides in an experimental group rendered diabetic by streptozotocin administration. The diabetic group showed a low plasma level of insulin compared with the control group: 0.5 ± 0.1 vs 3.5 ± 0.8 μg/l, (P< 0.01). Concomitantly, they exhibited clear glucosuria and a blood glucose level which was four times higher than in normal animals: 35.5 ± 1.4 vs 8.8 ± 0.8 mmol/l, (P< 0.001). The two peptide concentrations in the submandibular glands of diabetic rats showed an increase compared with controls: 42.9 ± 4.7 protein vs 24.7 ± 3.1 pg/mg protein (P< 0.001) and 34.9 ± 4.9 protein vs 18.4 ± 4.0 pg/mg protein (P< for insulin-like immunoreactivity concentration and somatostatin-like immunoreactivity concentration, respectively. Chronic insulin treatment of diabetic rats reversed the increase in somatostatin, but had no effect on the increase in insulinlike immunoreactivity concentration. A negative correlation (r = 0.24, P< 0.05) was found between the plasma insulin level and the somatostatin concentration of the submandibular glands. Our results suggest that the submandibular glands of rats may participate in the peripheral regulation of glucose homeostasis.