Interest rates remained little changed Wednesday morning with no major economic reports due to be released until next week. Shares of Fannie Mae and Freddie Mac tumbled for the second consecutive day on growing concerns over the likelihood of a federal bailout. The two beleaguered mortgage giants have $223 billion of bonds maturing by September 30. Their success in rolling over this debt may determine whether they can remain liquid. The companies have reported combined losses of nearly $15 billion over the past year.