Serum creatine kinase release and alpha- and beta-adrenergic receptors.

Changes in the serum creatine kinase (CK) activity and the mechanism of its release after administration of two kinds of beta-blockers to rats were studied in order to determine the mechanism of the increase in serum CK accompanying administration of beta-blockers. When pindolol or propranolol was administered at a dose of more than 10 mg/kg of body weight, the serum CK activity was increased in proportion to the dose. Also when an alpha-stimulator or an alpha, beta-stimulator such as noradrenaline and adrenaline was administered, the serum CK activity was increased. When the beta-stimulator isoproterenol or the alpha 1-blocker prazosin was administered, there was no increase in the serum CK activity. In terms of consecutive administration of a combination of beta-blockers and adrenaline, the serum CK activity was not increased by the second and succeeding administrations. As for the use of adrenaline alone, on the other hand, the serum CK activity after the second administration was equal to that after the first administration. The increase in CK activity after administration of adrenaline as the second treatment following administration of a beta-blocker as the first treatment was approximately the same as that after single administration of adrenaline. From the fact that the serum CK activity in rats was increased by administration of an alpha-stimulator and of a beta-blocker, it is possible that CK release in the blood is due to the action of alpha-receptors rather than beta-receptors. In the case of consecutive administration of a beta-blocker, the serum CK activity was not increased after the second administration. However, the serum CK activity was increased by the administration of an alpha-stimulator. This finding suggests the possibility that CK release is due to the disturbance of the balance between alpha-receptor and beta-receptor. Most of the CK isoenzymes released in the blood after administration of a beta-blocker were of the MM type.