Contribution of alkaloid fraction to pressor and hyperglycemic effect of crude Ephedra extract in dogs.


Harada M, Nishimura M




J Pharmacobiodyn


In anesthetized dogs, pressor and hyperglycemic effects of Ephedra aqueous extract as well as its alkaloid fraction and adsorption of alkaloid from the digestive tract were studied in order to investigate how closely effects of the alkaloid fraction relate to those of the Ephedra extract itself. Blood pressure, heart rate, and blood glucose concentration were increased by intraduodenal administration of the extract and the alkaloid fraction on the bases of the same alkaloid content (20 mg/Kg). In respect to the pressor and hyperglycemic effects, changes in time course of the effects produced by these two drug preparations were similar and in either of the two physiological parameters the maximal value given by the extract was about a half that given by the alkaloid fraction. A maximal level of blood pressure and blood glucose concentration was reached 10-15 min after the administration of the two drug preparations, while the amount of alkaloid absorbed in the portal vein until this time was about 2-3 times as much under administration of the alkaloid fraction as under administration of the extract. Absorption of alkaloid in the extract occurred slowly and lasted longer compared with that of the alkaloid fraction itself. On the contrary, the alkaloid-free extract administered intraduodenally showed no virtual effects on blood pressure and blood glucose concentration except producing tachycardia. It seems that the effect of Ephedra extract on blood pressure and blood glucose concentration was mostly qualitatively and quantitatively represented by that of alkaloid contained and that effect of the extract mainly depended on that of alkaloid absorbed early after its application.