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Stimulation of rat liver glycogenolysis by vitamin B6: a role for adrenal catecholamines
C A Lau-Cam1, K P Thadikonda, B F Kendall
1Department of Pharmaceutical Sciences College of Pharmacy and Allied Health Professions St. John's University Jamaica, NY 11439.
Abstract:
The administration of a single, 100-300 mg/kg ip, dose of a B6 vitamer to rats resulted in an almost immediate and gradual mobilization of the liver glycogen and a concomitant elevation of the serum glucose, with the order of potency being pyridoxal greater than pyridoxamine greater than pyridoxine. Since the B6 vitamer also stimulated the secretion of adrenal catecholamines and the accumulation of liver cAMP, and a pretreatment with selected blocking agents conferred significant protection against the glycogen depletion in the order of potency propranolol + phentolamine greater than propranolol greater than verapamil greater than phentolamine, a role for an adrenomedullary catecholamine-stimulated, beta-adrenoceptor-mediated, activation of the glycogen cascade system was suggested. This assumption was confirmed by verifying pyridoxal to possess virtually no effect on the liver glycogen of adrenalectomized rats.