Standard & Poor's lowered its rating on International Shipholding Corp.'s (ISC) $110 million 7.75% senior unsecured notes due Oct. 15, 2007, and $100 million 9% senior unsecured notes due July 1, 2003. The corporate credit rating on the company is affirmed. The downgrade on the notes is based on the increased proportion of secured debt in the company's capital structure, which has been used to finance the acquisition of additional vessels(primarily car carriers) over the past year and which effectively ranks senior to the unsecured notes. Previously, the unsecured notes carried a rating equal to the corporate credit rating, as the proportion of secured debt was less material. ISC's ratings reflect a substantial number of stable, intermediate- to long-term ship charter agreements, with credit quality constrained by fairly high debt leverage on a modest capital base and some exposure to the more volatile scheduled shipping business, S&P said.