Involvement of β₁-adrenergic receptors in regulation of the phosphorylation state of rat parotid gland proteins

Abstract

In the rat parotid gland, stimulation of its β-adrenergic receptors causes alterations in the phosphorylation state of three endogenous proteins (17, 19, and 30 kDa). The β-adrenergic receptors involved were characterized. Rat parotid slices were prelabeled with [³²P]orthophosphate and incubated with several concentrations of l-norepinephrine, l-epinephrine, and l-isoproterenol. The three catecholamines increased the ³²P content of the 19 and 30 kDa proteins and decreased that of the 17 kDa protein with the potency order of l-isoproterenol > l-norepinephrine ≥ l-epinephrine. Practolol was more potent in blocking the l-isoproterenol-induced alterations in the ³²P content than butoxamine. These results indicate that β₁-adrenergic receptors are involved in regulation of the phosphorylation state of the three parotid gland proteins, supporting the view that at least one of the three proteins is involved in parotid amylase secretion that is also regulated through β₁-adrenergic receptors.