Effect of isoproterenol on tyrosine hydroxylase activity in Mouse submaxillary glands.

The activity of tyrosine hydroxylase in the sub-maxillary glands was measured in mice treated with isoproterenol, a sympathomimetic amine which acts predominately on beta-receptors. The purposes were to determine whether chronic injections of isoproterenol would affect the activity of this enzyme and to attempt to gain some information about the mechanism of its affect. Chronic administration of the drug at dose of 100mg/kg (given once on day 0 and day 4 and twice on days, 1, 2, and 3) decreased the activity of tyrosine hydroxylase. The drug also increased amylase activity and protein content. Preliminary data indicate the isoproterenol decreases the Vmax of tyrosine hydroxylase and increases the Km for the pteridine cofactor.