CHRONIC BLOCKADE OF ENDOGENOUS FORMATION OF HYDROGEN SULFIDE CAUSED INCREASE IN SYSTEMIC BLOOD PRESSURE IN RATS

Hydrogen sulfide (H 2 S), an endogenous vasodilator, is produced by two enzymes; cystathionine γ‐lyase (CSE) and cystathionine β‐synthase (CBS). In this study, the effects of chronic inhibition of CSE by DL‐propargylglycine (37.5 mg/kg/day; ip) and CBS by aminoxyacetic acid (8.8 mg/kg/day; ip) given either alone or in combination for 4 weeks on systemic blood pressure (SBP) and renal function were examined in rats (n=6 in each group). Prior to the start and then every 7 th day during treatment period, SBP was measured by tail‐cuff method and 24 hr urine collections were made using metabolic cages. Urinary excretion rate of sulfate (U S V; marker for endogenous H 2 S level) was determined by a colorimetric assay. At the end of treatment period, rats were subjected to acute experiments under anesthesia for determination of renal blood flow (RBF; Transonic flow‐probe) and glomerular filtration rate (GFR; inulin clearance). Compared to vehicle treated group, only the combined therapy group showed a decrease in U S V (553±71 vs 248±50 nmol/24hr) and an increase in mean SBP (107±3 vs 130±2 mmHg) with its consequent increase in sodium excretion (4±1 vs 13±3 mmol/24hr). This group with combined therapy also showed a decrease in RBF (7±0.4 vs 4±0.3 mL/min/g) but not appreciably in GFR (1.0±0.1 vs 0.9±0.03 mL/min/g). These data suggest that a decrease in endogenous H 2 S production exerts direct vascular effect leading to an increase in SBP.