Snapping its three-session gaining string, the rupee has lost a massive 51 paise to end at 54.77 rupees against the US dollar due to fresh heavy demand for the American currency from importers and some banks amid weak local equities.The rupee opened a lower at 54.27 rupees from Friday's close of 54.26 rupees at the Interbank Foreign Exchange (Forex) market and immediately touched a high of 54.24 rupees on initial rally in domestic stocks amid sustained dollar selling by exporters. However, it turned negative after weakness in equities in late morning deals and declined further to a low of 54.79 before concluding at 54.77, a fall of 51 paise, or 0.94 per cent. In the last three sessions, rupee had gained 147 paise, or 2.64 per cent.