Tokyo stocks opened lower Friday as export-related issues were sold after the yen strengthened against the U.S. dollar. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average fell 135.22 points, or 0.37 percent, from Thursday to 36,698.05. The broader Topix index was down 15.26 points, or 0.59 percent, at 2,577.24. On the top-tier Prime Market, decliners were led by rubber product, transportation equipment and insurance issues. At 9 a.m., the dollar fetched 141.51-52 yen compared with 141.74-84 yen in New York and 142.74-76 yen in Tokyo at 5 p.m. Thursday. The euro was quoted a…