eng Oriental Scientific Publishing Company Biomedical and Pharmacology Journal 0974-6242 2025-06-30 18 2 1580 1589 10.13005/bpj/3195 66094 article Abdisalim A. Zaripov 3 Inoyat Z. Zhumaev 1 Pulat B. Usmanov 1 Yulduzkhon T. Mirzaeva 1 Shavkat Yu. Rustamov 1 Sadriddin N. Boboev 1 Institute of Biophysics and Biochemistry, National University of Uzbekistan, Tashkent, Uzbekistan. Institute of the Chemistry of Plant Substances, Uzbek Academy of Sciences, Tashkent, Uzbekistan. Uzbek State University of Physical Education and Sports, Chirchiq, Uzbekistan. The development of cardiovascular diseases is primarily associated with impaired activity of ion transport systems that ensure Ca²⁺ homeostasis in vascular smooth muscle cells. Modulation of the function of Ca²⁺ ion transport systems in smooth muscle cells with biologically active compounds allows the development of new approaches to the pharmacological regulation of Ca²⁺-dependent processes in cardiovascular diseases. This article studies the mechanisms of the vasorelaxant effect of the isoquinoline alkaloid 1-(3¢-Bromo-4¢-hydroxyphenyl-5¢-methoxyphenyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline hydrochloride (F-19) on the force of aortic ring contraction. It was found that the alkaloid F-19 exerts a concentration-dependent (5-100 μM) potent vasorelaxant effect on the force of aortic ring contraction induced by KCl and PE. The involvement of the L-type Ca²⁺ channel in the vasorelaxant effect of the alkaloid F-19 was investigated under conditions of incubation with its specific blocker verapamil. It was found that the role of the L-type Ca²⁺ channel in the vasorelaxant effect of this alkaloid is minor. The effect of the alkaloid F-19 on Ca²⁺ transport systems in the SR was also investigated. In this case, PE and caffeine-induced transient aortic contraction in the absence of Ca²⁺ significantly reduced. At the same time, a decrease in the vasorelaxant effect on aortic contractility was observed under the conditions of incubation with the SERCA inhibitor CPA, the alkaloid F-19. The vasorelaxant effect of the alkaloid F-19 on rat aortic smooth muscle contractility is mediated by several complex mechanisms. The vasorelaxant effect of this alkaloid is provided by inhibiting the entry of Ca²⁺ ions into the cytosol through plasma membrane potential-dependent L-type Ca²⁺ channels and the exit of Ca²⁺ ions into the cytosol through the SR Ca²⁺ transport systems, and by activating SERCA. https://biomedpharmajournal.org/vol18no2/mechanism-of-vasorelaxant-action-of-isoquinoline-alkaloid-f-19-on-rat-aorta/ Alakaloid Ca-channels endothelium nitric oxide smooth muscle