For the second time this week, Hong Kong mopped up China's losses in Asia trading Thursday as Beijing regulators announced they were considering allowing share swaps between dual-listed Chinese companies. Such swaps would be a positive for Hong Kong "H" shares, but are a negative for the higher-priced Chinese "A" shares.The news sent the Shanghai Composite diving 175 points below its new 6,000 benchmark, ending the day down 3.5% at 5,825.28. Conversely, after opening above a record 30,000 for the first time, the Hang Seng ended the day up 166 points, or 0.57%, to 29,465.05. "Market sentiment was obvious today," says Conita Hung, head of equities at Delta Asia Finance Group in Hong Kong. "This type of action will have more impact on Chinese 'A' shares than Hong Kong 'H' shares at the moment." Currently, companies with listings on both the Hang Seng and the domestic Chinese markets trade at about a 68% premium on the mainland. The disparity in prices is caused by the limited investment options available to Chinese investors and the lack of derivatives products there, making short selling the China shares impossible. Gainers in Hong Kong included PetroChina ( PTR), up 1.39% to HK$18.92, China Life Insurance ( LFC), which bounced 0.98% to HK$51.30, and China Unicom ( CHU), jumping 1.51% to HK$16.12. All three companies hit record highs in Hong Kong, but in Shanghai, China Life Insurance shares traded down for the second day, falling 1.75% to 67.98 yuan.