Release of kallikrein and tonin from the rat submandibular gland

The interaction of neurotransmitters and hormones with specific receptors on the plasma membranes of cells results in enzyme secretion from exocrine glands. However, the effects of agonists on the release of kallikrein and tonin from the rat submandibular gland have not yet been evaluated systematically. The purpose of the present study was to investigate the effects of norepinephrine, isoproterenol, methacholine, and cholecystokinin on the simultaneous release of kallikrein and tonin from the rat submandibular gland. Submandibular gland slices were incubated in vitro at 37 degrees C in a modified Krebs-Ringer medium containing 0.2% each of glucose and bovine serum albumin and bubbled with a gas mixture of 95% O2 and 5% CO2. Glandular kallikrein and tonin secreted into the incubation medium were determined by specific radioimmunoassays. Norepinephrine at 10(-5) M concentration increased kallikrein secretion from a control value of 7.7 +/- 1.5 to 114.7 +/- 26.9 ng/min/mg tissues (p less than .01), and at 10(-4) M concentration kallikrein secretion increased to 265.9 +/- 58.3 ng/min/mg tissue (p less than .01). Similarly, norepinephrine at 10(-5) M enhanced the release of tonin from a basal rate of 4.4 +/- 0.6 to 57 +/- 14.4 ng/min/mg tissue (p less than .05), and at 10(-4) M the rate increased to 91.3 +/- 20.0 ng/min/mg tissue (p less than .01). In contrast, isoproterenol, methacholine, and cholecystokinin did not increase the secretion of kallikrein or tonin. We conclude that the secretion of kallikrein and tonin from rat submandibular glands upon sympathetic stimulation is mediated through stimulation of alpha-adrenoceptors only.