Potassium release from the rat submaxillary gland in vitro. I. Induction by catecholamines

Area of Science:

• Physiology
• Pharmacology
• Cell Biology

Background:

• The submaxillary gland's secretory mechanisms involve complex ion transport.
• Adrenergic receptor signaling plays a crucial role in glandular function.

Purpose of the Study:

• To investigate the role of adrenergic receptors in potassium (K+) release from submaxillary gland slices.
• To elucidate the mechanisms underlying K+ release and reuptake.

Main Methods:

• In vitro incubation of submaxillary gland slices in Krebs-Ringer-bicarbonate medium.
• Stimulation with alpha and beta adrenergic secretagogues (norepinephrine, epinephrine, phenylephrine, isoproterenol).
• Monitoring of K+ release and effects of antagonists (phentolamine, propranolol) and inhibitors (ouabain, calcium chelators).

Main Results:

• Alpha-adrenergic agonists (norepinephrine, epinephrine, phenylephrine) induced K+ release, while beta-agonist (isoproterenol) did not.
• Norepinephrine-induced K+ release was dose-dependent and enhanced by substrate deprivation.
• Phentolamine (alpha-antagonist) reversed norepinephrine's effect, while propranolol (beta-antagonist) did not.
• Ouabain increased K+ release and blocked phentolamine's reversal.
• Calcium (Ca++) was essential for norepinephrine-induced K+ release, but did not induce release on its own.

Conclusions:

• Potassium release from the submaxillary gland is primarily mediated by alpha adrenergic receptors.
• Net K+ release results from opposing passive extrusion and active reuptake mechanisms.
• Active K+ reuptake is energy-dependent, mediated by the ouabain-sensitive Na+-K+ ATPase.
• The process critically depends on extracellular Ca++, likely involving Ca++ influx upon alpha-adrenergic stimulation.