The Smithsonian Institution, accepting a $45 million gift from the Donald W. Reynolds Foundation, announced yesterday that the two museums and other facilities in the Old Patent Office Building would be called the Donald W. Reynolds Center for American Art and Portraiture.

The Las Vegas-based foundation, now the second largest donor in the Smithsonian's history with a total contribution of $75 million, directed its new multimillion-dollar support to the renovation and exhibitions at the landmark building. The National Portrait Gallery and the Smithsonian American Art Museum, which are housed in the building at Ninth and F streets NW, will retain their individual names.

The decision marks the third time the Smithsonian has given major donors the privilege of having their names on a publicly funded national museum, a growing and controversial practice among many museums and performing arts centers that are looking for ways to acknowledge sizable donations in tight economic times.

The Reynolds money will "not only help restore this building to its past glory, but take it to an aesthetic and functional level which will, at long last, allow it to reach its full architectural potential," said Smithsonian Secretary Lawrence M. Small, at an upbeat news conference. "Our progress on this building has taken a great leap forward with this gift."