"NEW YORKÛÓEven though interest rates may not have hit bottom, some mortgage lenders are raising the rates they charge as homeowners rush to refinance their loans.</br></br>Some lending institutions are marking up mortgage rates because of the tide of refinancing applications, which gives them a pricing advantage, mortgage bankers say.</br></br>ÛÏWhen there is greater demand than supply, that is what any retailer would do,"" said John Sousa, president of Commonwealth Mortgage Co. in Burlington, Mass.</br></br>greater now than in a slow market,"" added Bill Brewster, assistant director at the Mortgage Bankers Association of America.</br></br>The national average for a 30-year, fixed-rate loan was 8.82 percent on Feb. 6, up from a recent low of 8,31 percent on Jan. 10, according to HSH Associates, a mortgage information firm in Butler, NJ."