Effects of cholinergic and α-adrenergic agonists on the monovalent ion content of rat submandibular gland acinar cells studied by X-ray microanalysis

 The effects of cholinergic and α-adrenergic stimulation (in vivo and in vitro) on the monovalent ion content of rat submandibular gland acinar cells were evaluated at the subcellular level by X-ray microanalysis. Fragments of glands or enzymatically dispersed acini were slam-frozen and cut into ultrathin cryosections. Spectra were collected from secretory granules, nucleus, the basal cytoplasm containing endoplasmic reticulum and the apical cytoplasm identified between secretory granules. No significant changes in Na and Cl content were observed after the isolation of acini, but the K concentration decreased compared with cells from in situ glands. The Cl and K content in all four compartments studied decreased significantly after cholinergic stimulation both in vivo and in vitro but in a more restricted fashion after α-adrenergic stimulation. Our findings indicate that: (1) the physiological mechanisms regulating the monovalent ion composition of submandibular cells are relatively well preserved in isolated acinar cells; (2) the results from in vivo experiments are in good agreement with those from in vitro experiments; and (3) the effects of cholinergic and α-adrenergic stimulation on the K⁺ and Cl^–efflux at the subcellular level are similar but the response is generally less with α-adrenergic stimulation. Accepted: 24 April 1997