U.S. Sen. Chuck Grassley, R-Iowa, Congress' leading critic of nonprofit abuses, has asked three of North Carolina's largest hospitals to share information about their use of a rapidly growing discount drug program, saying they don’t appear to be passing along the "massive" savings to patients. Instead, the discounts appear to be subsidizing "bottom line operating margins," Grassley wrote in a letter that was emailed Friday to the heads of Carolinas Medical Center, Duke University Health System and UNC Hospitals. The letters cite a recent investigation by the The Charlotte Observer and The News & Observer of Raleigh.