S-allylcysteine (SAC) is an organosulfur-containing compound derived from garlic. Studies have shown that garlic is beneficial in the treatment of
cardiovascular diseases. This study aims to elucidate if SAC is responsible for this cardioprotection using acute
myocardial infarction (AMI) rat models. In addition, we hypothesized that SAC may mediate cardioprotection via a
hydrogen sulfide (H(2)S)-related pathway. Rats were pretreated with saline, SAC (50 mg x kg(-1) x day(-1)), SAC + propagylglycine (PAG; 50 mg + 10 mg x kg(-1) x day(-1)) or PAG (10 mg x kg(-1) x day(-1)) for 7 days before AMI induction and killed 48 h after. Our results showed that SAC significantly lowered mortality (12.5% vs. 33.3%, P < 0.05) and reduced
infarct size. SAC + PAG- and PAG-treated rats had larger
infarct sizes than controls (60.9 +/- 0.01 and 62.0 +/- 0.03%, respectively, vs. 50.0 +/- 0.03%; P < 0.05). Pretreatment with SAC did not affect BP, but BP was significantly elevated in SAC + PAG and PAG-treated groups (P < 0.05). In addition, plasma H(2)S levels and left ventricular
cystathionine-gamma-lyase (CSE) activities were analyzed to investigate the involvement of H(2)S. CSE is the
enzyme responsible for H(2)S production in the heart. SAC increased left ventricular CSE activity in AMI rats (2.75 +/- 0.34 vs. 1.23 +/- 0.16 micromol x
g protein(-1) x h(-1); P < 0.01). SAC + PAG-treated rats had significantly lower CSE activity compared with the SAC-treated group (1.22 +/- 0.27 vs. 2.75 +/- 0.34 micromol x
g protein(-1) x h(-1); P < 0.05). Similarly, SAC-treated rats had higher plasma H(2)S concentration compared with controls and the SAC + PAG-treated group.
Protein expression studies revealed that SAC upregulated CSE expression (1.1-fold of control; P < 0.05), whereas SAC + PAG and PAG downregulated its expression (0.88-fold of control in both groups; P < 0.005). In conclusion, our study provides novel evidence that SAC is protective in
myocardial infarction via an H(2)S-related pathway.