Hsing-Hsing, the National Zoo's ailing giant panda, seems to be feeling better, zoo officials said yesterday. But the zoo is going ahead with a planned trip to China this month to try to negotiate for another pair of the popular, highly endangered animals.

The 28-year-old male panda -- the zoo's most visited attraction and one of the oldest of the species in the world -- popped out of his Panda House yesterday and also could be seen chewing on bamboo in his outdoor yard.

Hsing-Hsing (pronounced Shing-Shing) was diagnosed last month with irreversible chronic kidney failure, probably related to his advanced age. Although zoo officials said they do not know how long he will live, they said this is likely his final illness.

"He has surprised us with his ability to respond," said zoo veterinarian Lucy Spelman, who emphasized that this is not a deathwatch yet. "He's really tough."

For treatment, the zoo has anesthetized the panda four times in the past two weeks and given him intravenous fluids to counter dehydration and make him produce more urine to flush out toxins. The panda also is on anti-nausea medication to encourage him to eat and is on antibiotics to ward off infections.

Hsing-Hsing continues to receive anti-inflammatory medication for his arthritis, which may be aggravating his kidney problems. But Spelman said the zoo has no choice because without it the animal will not eat or move.

The zoo has ruled out dialysis as being too invasive and because Hsing-Hsing would have to be under anesthesia for several hours a day, a risk for such an elderly animal.

Hsing-Hsing, whose name means "shining star" in Chinese, began showing his age two years ago, around the 25th anniversary of his arrival with his mate, Ling-Ling. The pandas were a gift from the Chinese government after President Richard M. Nixon's visit to China, and the pair's attempts to breed were an annual spring soap opera for years.

The pandas produced several cubs, but none lived more than a few days. Ling-Ling died in 1992 of age-related heart failure.

Hsing-Hsing's first sign of ill health was arthritis. Then he developed cancer in one testicle, forcing vets to remove both as a precaution.

A year ago, zoo officials began quiet talks with the Chinese to try to get another panda pair. A team of zoo officials will make a previously scheduled visit to China this month and "hopefully come back with an agreement signed," said Devra G. Kleiman, a senior research scientist and panda expert.

But efforts to bring new giant pandas to Washington have bogged down over financial arrangements and are subject to a veto by senior Chinese leaders, according to a Chinese official in charge of international panda exchanges.

China carefully doles out pandas, offering them on loan for a steep fee intended to fund conservation efforts. The current charge is $1 million per pair a year.

"This is the lowest donation figure acceptable to all the parties within China," said Zhao Qingguo, an official from the Ministry of Construction who oversees panda exchanges. "We want to protect the pandas. We don't want the price, or the donation we ask for, to be very flexible. If that was the case, people would think it was like a business transaction. . . . We won't bargain."

Kleiman said the government-affiliated National Zoo cannot quickly raise the amount of money that private zoos in the United States can. "Our Chinese colleagues know this," she said, and have taken that into consideration in the discussions.

Four separate Chinese government bodies -- the Construction Ministry, Forestry Bureau, Foreign Ministry and China's cabinet -- must approve each panda loan. The zoo also must obtain a panda import permit from the U.S. Fish and Wildlife Service and adhere to a research protocol agreed to by American zoos.

The Chinese government lent two pandas to the San Diego Zoo in 1996 on a 12-year contract. San Diego pays $1.2 million a year and shares insights gleaned from behavioral and other research. The San Diego pair has not had a cub.

Any loan of pandas must be approved by senior Chinese leaders, and the recent downturn in Sino-American relations may scuttle any deal.

"Pandas are China's national symbols. They are tokens of friendship and are themselves priceless," said Wang Weiming, head of the Beijing Zoo's panda department. "The most important thing is to see the American government's attitude."

Asked whether new pandas might be sent to Washington, Wang replied: "You have to ask [Chinese President] Jiang Zemin. . . . He's the person who would decide."

Pandas are native to the forests of China. Fewer than 1,000 are believed to be alive worldwide, including those in Berlin, Mexico City, Paris and Tokyo zoos.

Hsing-Hsing's local fans are following his illness closely. Some called the zoo yesterday, suggesting blueberries or other treatments as kidney cures.

At the Panda House yesterday, two dozen sixth-graders from the Richmond suburb of Midlothian, making their annual school visit to the panda, sat quietly on the floor as mammal curator Lisa Stevens talked about panda biology.

"He's out!" someone shouted. Students rushed to the railing, pulled out disposable flash cameras and lined up five deep on tiptoes for a look. As his admirers watched, Hsing-Hsing lumbered across the floor, leaned against a wall and sat down, his hind legs splayed out in front of him. He grasped a stem of bamboo in his paws, nibbling slowly.

"He's soooo cute!" said Shannon Taylor, 12.

"I just wish he'd look better," said classmate Brittany Hersman, 11. "He didn't look very happy."

To read get-well wishes for Hsing-Hsing, see washingtonpost.com and click on Metro. Daily updates on his condition are available at www.si.edu/natzoo.

Assessing Hsing Hsing

Hsing Hsing, the National Zoo's beloved giant panda, was diagnosed last month with chronic kidney failure. The 28-year-old panda will be treated for this and other existing health conditions.

Hsing Hsing's state of health

April 1997: Diagnosed with arthritis in spine and front limbs. Treated with anti-inflammatory medication, which he continues to take.

April 1997: Diagnosed with testicular cancer. The cancer and both testicles were removed; no further signs of the disease have been detected.

May 1999: Diagnosed with kidney dysfunction after a period of lethargy and weight loss.

Treatment options

Dialysis has been ruled out, as it would require Hsing Hsing to be anesthetized every day for several hours, which is dangerous for an older animal. In the wild, giant pandas live about 15 years. At 28, Hsing Hsing is believed to be one of the oldest giant pandas in the world.

Kidney transplant is not a viable option because of the lack of donors. It is estimated that there are fewer than 1,000 pandas left in the wild. Nearly all of the 125 or so captive pandas live in China. The United States has only three: Hsing Hsing and Shi-Shi and Bai Yun at the San Diego Zoo.

Fluids and medication can help stabilize Hsing Hsing's condition and keep him comfortable. So far, this has been effective treatment.

SOURCE: National Zoo

CAPTION: Though ailing from chronic kidney failure, Hsing-Hsing ventured out of the zoo's Panda House yesterday.

CAPTION: Hsing-Hsing made a small comeback after worrying National Zoo officials. "He's really tough," one veterinarian said of the 28-year-old panda.