The Depository Trust & Clearing Corp. said that despite the downgrading of the U.S.'s credit rating by Standard & Poor's, it will not alter the valuations of Treasurys it holds in its facilities. The DTCC told traders that they will not be required to post more Treasurys to maintain their collateral levels on outstanding trades. The DTCC did say the National Securities Clearing Corporation is adding "intra-day" margin calls in an effort to deal with increased market volatility and to lower counterparty risks. Standard & Poor's has cut the ratings on National Securities Clearing Corp., Fixed Income Clearing Corp. and Depository Trust Co. to AA+. The entities are subsidiaries of Depository Trust & Clearing Corp. S&P also downgraded Options Clearing Corp., the clearer for all nine U.S. options exchanges. Recent events make SIFMA's Market Structure Conference a must-attend event, register today.