Madison Avenue is staying tuned to “Ellen” these days as the ABC sitcom begins dropping hints its title character may be a lesbian.

Advertising buyers say some sponsors may avoid the show if Ellen comes out of the closet, but they suspect ABC could find others to step in. The reaction, they say, depends on how the issue is handled.

If Ellen gets a girlfriend and “the two of them are going to the zoo together, it’s not a problem,” said Paul Schulman, who specializes in buying network advertising time. “If they are in bed together, it’s a problem.”

The series has become the television season’s hottest topic of conversation since TV Guide reported last week that the lead character, played by Ellen DeGeneres, might come out as a lesbian this season.

While gay characters have been turning up more frequently in supporting roles on TV, no network show has ever had a homosexual central character.

The season’s opening episode on Wednesday night heightened speculation that the series may be headed in that direction.

In the episode’s opening scene, Ellen Morgan, having just awakened and looking frowzy in her robe, serenades herself in the bathroom mirror: “I feel pretty, I feel pretty, I feel pretty and witty and -” where-upon she dips her toothbrush under the faucet, only to discover there’s no water. Instead of completing the lyric as written - “gay”- she says, “Hey!”

Later in the show, a real estate agent showing Ellen and a friend slides of new homes holds a girl doll against the screen and says, “Just think, Ellen, this could be you, walking up to your new home.” Then the agent produces a boy doll, and says: “And here’s your husband coming home from work.”

“Oh, I think that puppet’s in the wrong show,” Ellen replies.

ABC said there have been no defections among advertisers since the TV Guide report.

Gene DeWitt, who heads his own media buying service, said companies are more aware of the economic muscle of the gay community and pursue that audience.

“I wonder if, except for a few overly sensitive advertisers, whether it really is an issue,” he said.