Contrast medium is essential for diagnosis of many diseases. However, recent studies showed that contrast agents can induce renal injury and is associated with poor long-term clinical outcome, especially in diabetes. To date, no data are available on the relationship between contrast medium and endothelial function. Endothelial dysfunction is known to precede atherosclerosis and is considered a risk marker for future development of cardiovascular disease. Therefore, we hypothesized that contrast agents may induce endothelial dysfunction in healthy men. In addition, we hypothesized that contrast induced endothelial dysfunction via free radicals. Thus, we also test alpha-lipoic acid whether or not protect endothelial dysfunction induced by contrast agents.

Inclusion Criteria:

• healthy men
• 20 yr < = age < = 30 yr
• 20 < = body mass index < = 25

Exclusion Criteria:

• age < 20 yr or > 30 yr
• dysfunction for liver, renal, and heart.
• other diseases such as diabetes, hypertension, thyroid disease