The losses in Asia on Friday were paced by financial stocks with direct exposure to the U.S. subprime mortgage market, which lends money to people with poor credit records.
'To pace' means to set or regulate the pace for. What this sentence is saying is that the financial stocks with direct exposure to the U.S. subprime mortgage market set the pace from the losses in Asia. In other words, those financial stocks were the ones most responsible for the decline in the Asian market.