First Lady Nancy Reagan is expected to give an official endorsement early next month to an 11-hour antidrug rock concert that will be broadcast by satellite to 150 nations, including the Soviet Union. Titled the Concert That Counts, the April 26 event, at a location yet to be decided, will include some of the biggest rock stars, according to the Los Angeles Times.

Since it is not a fund-raising concert, the big acts will be paid to perform. The purpose of the event is to deglamorize drug and alcohol use by showing big-name rock stars who do not indulge. The Pointer Sisters and Toto have signed up and on March 3 it will be announced which other stars will participate. Global Media Inc., the organizer, hopes to hold the concert at the Rose Bowl, but neighbors have protested. Alternative sites are the Los Angeles Memorial Coliseum and the Pontiac, Mich., Silverdome. END NOTES

The various charity auction fundraisers around town try to outdo themselves each year by having a special item that will surely attract attention -- for example, an antique automobile or a round trip to some exotic port. The Georgetown Preparatory School hasn't come up with that kind of glittery exotica. It is offering a 900-pound Black Angus steer, live or boxed. Now who could accept it boxed? If you brought it home to Georgetown or Potomac, it would make a trend-setting pet. Besides, red meat isn't good for you . . . Royal Watch:

Prince Charles left for home yesterday after resting up in the refined comforts of the Annenbergs' palatial Rancho Mirage, Calif., estate. After his whirlwind five days in Texas celebrating the state's 150th birthday, the traveling prince came to the home of former ambassador to the Court of St. James's Walter Annenberg and his wife Leonore, former U.S. chief of protocol, for some sunshine and polo. The team Charles rode with Saturday won the match and Frank Sinatra's wife Barbara presented the prince with a trophy. Charles said he needed the exercise badly "and my liver needs it even more so." Then he quickly added: "They have very good food in Texas." Nice catch, Charles. Those Texans don't take kindly to such aspersions on their cuisine . . . Royal Watch, Pacific Theater:

Meanwhile mom Queen Elizabeth and dad Prince Philip are in Auckland, New Zealand, where yesterday the queen was hit in the leg with an egg thrown by a young woman protesting her visit. Another young woman threw an egg that hit the royal car. The queen appeared visibly upset by the attacks. There is also the possibility the Royal Couple may face, so to speak, a traditional Maori insult called "whakapohane:" a "21-bum salute," the baring of buttocks. If the whakapohane ever catches on here, it won't be safe for politicians to go out in public again . . .

Fiscal cutbacks are creating a new kind of social activist. Beginning March 9, the Library of Congress will be closed on Sundays and evening hours will be all but eliminated, making it truly a service available virtually to only Congress. Librarian of Congress Daniel J. Boorstin has expressed his concern, and tonight a candlelight vigil of students, professors and representatives of the blind will gather in front of the Jefferson Building. And even social activist for the homeless and hungry Mitch Snyder said he might attend . . .