Tokyo stocks ended slightly lower Tuesday as investors locked in gains after recent 34-year highs of key indexes, although losses were limited by buying of export issues on a weaker yen. The 225-issue Nikkei Stock Average ended down 106.77 points, or 0.28 percent, from Monday at 38,363.61. The broader Topix index finished 7.39 points, or 0.28 percent, lower at 2,632.30. On the top-tier Prime Market, decliners were led by insurance, pulp and paper, and farm and fishery issues. The U.S. dollar remained firm in the lower 150 yen range, supported partly by buying from domestic importers, dealers s…