American teen-agers, frequently wielding parents' firearms, are killing themselves in "epidemic" numbers, suicide experts said here last week.

New York Lt. Gov. Alfred DelBello joined a panel of the experts in calling for a national commission and research program to isolate reasons for the virtual tripling in the suicide rate for 15- to 24-year-olds since 1950. The shift accounts for one teen-age suicide every two hours -- more than 6,000 last year -- and an attempt every minute.

Only accidents are cited as a more frequent cause of death among youth.

"We study fish and we study frogs. We even study Frisbees. But we don't know anything about our kids," said DelBello, founder and a chairman of the National Committee on Youth Suicide Prevention. "Somebody has got to start painting the picture on a national basis."

"We have to stop rushing for an answer," actor Peter Fonda, whose mother committed suicide when he was 10, told a forum of 600 persons.

"I'm trying to take the 'why' out. 'Why' is looking for too quick an answer. 'What is going on' is a slower approach. It may take extensive asking," Fonda explained in an interview.

Only since 1978, when new statistics on suicides were published, have experts become aware of the dimensions of the problem, according to American University psychologist Alan Berman, president of the American Association of Suicidology.

"Cluster suicides," strings of conceivably "copycat" suicides in upstate New York, Clear Lake and Plano, Tex., and outside San Mateo, Calif., attracted nationwide attention but so far have yielded few clues, Berman said.

"The reality is we're just beginning to study this," he said.

Boston psychologist Pamela Cantor cited increasing child abuse, fear of nuclear attack, alcoholism and family dissolution as causes for suicidal behavior.

More and more, however, the availability of firearms in a house contributes to teen-age suicide; nearly two-thirds of teens who kill themselves use guns, and four-fifths of them use handguns, according to experts.

Berman said he sees a correlation between increased firearm ownership and teen-age suicide. "Please get guns out of the house," urged Cantor, who with DelBello termed the suicide rate among young people an "epidemic."

DelBello said, "Children have to understand this suicidal feeling is part of life. We have to bring that out . . . . They're not afraid of the subject. We are."

Donna-Marie Buckley of Wappinger Falls, N.Y., said her son hanged himself last May. "Ponder me this: How can we help them if they're dead? We need help for research. We need funding. That's it," she said.

Two grandparents leaving the forum said their granddaughter, an adoptee with an older, favored stepsister, had tried on several occasions to kill herself by slitting her wrists.

"When they spoke of blood, this really sent chills through me," the grandmother said. "She's crying for help and starting to get it. We know we have to keep her alive."