Transport of calcium in the perfused submandibular gland of the cat.

1. In the perfused cat submandibular gland efflux and influx of (45)Ca, and concentrations of K, (40)Ca and Mg in the effluent from the gland were measured under different experimental conditions.2. When the standard perfusion fluid was shifted to a high Mg (5 mM) or a low Ca (0.25 mM) solution the efflux of (45)Ca from the pre-labelled gland declined. The magnitude and the duration of the effect of the high Mg concentration was more marked at a low external Ca concentration and was abolished by Mersalyl (1 mM). When the standard perfusion fluid was shifted to a Mg-free solution the efflux of (45)Ca from the pre-labelled gland increased.3. After shift of (45)Ca containing perfusion fluid from normal to a high Mg (5 mM) solution the influx of (45)Ca to the gland increased rapidly.4. Both acetylcholine (ACh) and adrenaline caused a marked increase in the efflux of (45)Ca from the pre-labelled gland. This increase in efflux was also seen under conditions where the gland was unable to secrete, i.e. during perfusion with Ca-free and Na-free tetraethylammonium Locke solutions.5. Stimulation with ACh failed to reveal any rapidly occurring increase in influx of (45)Ca.6. Stimulation with ACh evoked a small temporary increase in the concentration of (40)Ca. and Mg in the effluent.7. It is suggested that Ca uptake by intracellular Ca-accumulating systems of the submandibular gland depends on the external Mg concentration and that ACh and adrenaline cause a release of Ca bound intracellularly.