Heterodimeric phospholipase A2 HDP-1 from the venom of Nikolsky viper consists of two noncovalently bound subunits-HDP-1P and HDP-1In, the first of which exhibits lipolytic activity, while the second does not. The subunits have similar molecular masses and amino acid sequences. Administration of HDP-1 and HDP-1P to anesthetized rats is accompanied by prolonged hypotensive effects, the intensity of which depends on the dose. After the administration of HDP-1P, the effect develops more slowly than in the case of HDP-1, containing both subunits, while individual HDP-1In does not affect hemodynamic parameters. It was found using electrocardiography that HDP-1 and HDP-1P affect the functioning of the rat heart, causing arrhythmia, which may indicate their ability to affect the innervation of the heart. The administration of HDP-1 and its subunits also leads to changes in blood biochemical parameters, indicating their damaging effect on cells and internal organs.