Ion transport and signalling in human labial glands

Recent reports characterizing the physiological properties of normal human labial acini are reviewed with particular emphasis on mechanisms related to fluid secretion. In contrast to the salivary glands of several experimenta l animals, human labial acinar cells do not appear to have al-adrenergic re ceptors, substance P peptidergic receptors, or significant levels of Cl-/HC O3- exchange. Nor do they appear to secrete HCO3- in response to Ca2+ mobil izing stimuli. The data presently available indicates that fluid secretion by these glands is mainly under muscarinic control and is due to acinar Cl- secretion driven by a basolateral Na+-K+-2Cl(-) cotransporter.