LAUSR

Thyroid hormones have a role in the regulation of hydrogen sulfide (H2S) biosynthesis. In this study, we determined the effects of hyperthyroidism on H2S levels in various tissues and messenger RNA (mRNA) expression of cystathionine‐β‐synthase (CBS), cystathionine‐γ‐lyase (CSE), and 3‐mercaptopyruvate sulfurtransferase (3‐MST) in the liver and muscles of the rat. Sixteen male Wistar rats were divided into the hyperthyroid and the control groups. Hyperthyroidism was induced by adding l‐thyroxine (12 mg/L) to drinking water for a period of 21 days. H2S concentrations in serum, liver, aorta, heart, and soleus muscles, as well as mRNA expressions of CBS, CSE, and 3‐MST in these tissues were measured at Day 21. Hyperthyroid rats had lower H2S levels in the serum compared with controls (14.7 ± 1.4 vs. 25.7 ± 1.6 µmol/L, p < 0.001). Compared with controls, hyperthyroid rats had lower levels of H2S in the aorta (89%), heart (80%), and soleus (103%) muscles, but higher levels in the liver (35%). Hyperthyroidism decreased the ratio of CBS/CSE mRNA expression in the liver and the CSE/CBS mRNA expression in the muscles by decreasing CBS levels in liver (34% cf. controls) and CSE levels in the aorta, heart, and soleus muscles (respectively, 51%, 7%, and 52% cf.). In addition, hyperthyroidism decreased the mRNA expression of 3‐MST in the liver (51%) and aorta (33%), and increased it in the heart (300%) and soleus muscle (182%). In conclusion, hyperthyroidism increased H2S levels in the liver and decreased it in muscles; these effects are at least in part due to increases and decreases in expression of CSE in the liver and muscles, respectively. These data indicate an association between thyroid hormone status and gene expression of the H2S‐producing enzymes in the rat.