The variations in the intracellular free calcium concentration, [Ca2+]i, have been studied in isolated acini of rat parotid gland with a fluorescent probe, fura-2. In unstimulated acini, [Ca2+]i amounted to a basal value of 180 nM. Isoproterenol used at a concentration of 200 microM, in the presence of a beta-adrenergic blocker, caused a net increase of [Ca2+]i to a mean of 90 nM above basal values. This increase was suppressed by phentolamine, an alpha-adrenergic blocker. A weak increase of [Ca2+]i of 47 nM was also obtained when acini were incubated with 1 microM isoproterenol. This effect was suppressed with 0.1 microM propranolol which, at this concentration, specifically antagonizes the beta-adrenergic receptors. We conclude that isoproterenol at 1 microM, increases the [Ca2+]i by stimulating beta-adrenergic receptors. This effect is not reproduced by forskoline. Our results suggest that this isoproterenol effect on [Ca2+]i is independent of the formation of cyclic AMP. Moreover, when the isoproterenol concentration is high (200 microM), the increase of [Ca2+]i could be through an activation of alpha-adrenergic receptors.