“…Synergistic effect of H 2 S with NO on vascular relaxation led to the identification of two mechanisms (Hosoki et al, 1997). One is that the chemical interaction between H 2 S and NO produces H 2 S n , nitosothiol, thionitrous acid (HSNO), and nitrosopersulfide (HSSNO) that have the relaxation effect greater than each parental molecule (Nagai et al, 2006;Whiteman et al, 2006;Oosumi et al, 2010;Filipovic et al, 2012;Ebenhardt et al, 2014;Stubbert et al, 2014;Cortese-Krott et al, 2015;Moustafa and Habara, 2016;Miyamoto et al, 2017; See also Kimura, 2020). Another mechanism is that H 2 S and NO mutually regulate their synthesizing enzymes (Zhao et al, 2001;Minamishima et al, 2009;Kondo et al, 2013;King et al, 2014;Kimura, 2016).…”