Three alleged Washington drug dealers were arrested and held on highly unusual second degree murder charges yesterday in connection with the overdose death last year of a man who had taken an extremely potent brand of heroin known to users and sellers as "First Degree."

Two other persons also were arrested and nine others were being sought on various drug charges yesterday. They too were alleged to have been involved in the sale of the highly potent heroin, which authorities said caused as many as 10 overdose deaths here when it was commonplace on the streets last fall.

The murder charges against the alleged dealers stem from the overdose death last November of James Owens, 27, who died Nov. 3 after taking a quantity of "First Degree" in an apartment on 12th Street SE.

Arrested on the murder charges, after what was described as an 11-month investigation, were Leonard C. McRae, 37, of 242 W Street NW; Douglas E. Ward, 23, of 231 18th St. SE; and Reginald Anthony Lucas, 35, of 531 14th St. SE, police said.

Assistant U.S. Attorney Roger M. Adelman said at McRae's bond hearing that McRae "directed the operation that distributed heroin at Potomac Gardens," the Southeast housing project around which the overdose deaths last fall--including that of James Owens--were clustered.

U.S. District Court Magistrate Arthur L. Burnett ordered McRae held in lieu of $60,000 surety bond. He is charged with conspiracy to sell heroin and sale of heroin, in addition to the murder charge.

McRae's court-appointed attorney, Sol Z. Rosen, told Burnett that "even from Adelman's cryptic statement . . . McRae's involvement is totally tangential and speculative."

Rosen said after the hearing that McRae "denies any involvement in the whole transaction" and that "the government is going to have an exceptionally hard time proving causality" or linking McRae to Owens' death.

Lucas, who faces charges of second degree murder, possession of heroin and conspiracy to sell heroin, was ordered held in lieu of $25,000 bond. Ward, who was charged with second degree murder and conspiracy to sell heroin, was ordered held in lieu of $10,000 bond.

The two other persons arrested yesterday--Carolyn Toms, 35, of 3694 Hayes St. NE, and Leroy P. Clay, 57, of 1000 12th St. SE--were charged with conspiracy to distribute heroin. Toms was released on personal recognizance and Clay was released on $10,000 personal bond.

Police believe that of 10 to 12 people who died of overdoses in the District last fall, "some or all of those deaths were caused by 'First Degree' heroin," Adelman said during one hearing yesterday.

McRae allegedly cut and packaged the heroin under that trade name, Adelman said in court, and used at least a dozen or so assistants and runners to distribute what Adelman said was the "most favored" variety of heroin among users in the Potomac Gardens area of near Southeast, not far from the Marine Barracks.

Narcotics detectives yesterday said that "First Degree" heroin was at least 15 percent pure, compared with an average 5 percent purity for heroin sold on the street.

McRae allegedly kept in contact with runners by a beeper system, Adelman said, and when street salesmen needed more heroin, McRae would "lickety-split appear on the scene with more heroin."

Adelman said during the hearing that Owens got the heroin from Ward and Lucas. "Ward said it was powerful stuff--don't shoot it all at once," Adelman said.

"Owens shot it up," and died as a result, Adelman said, adding that the government had witnesses who would testify that the heroin that killed Owens came from McRae.

Washington led the nation in heroin deaths per capita in 1981 with 114 recorded deaths. But the rash of 10 deaths in a 10-day period in the fall of last year surprised veteran narcotics detectives and led to the investigation that resulted in yesterday's arrests.

None of the other nine suspects being sought in the case is expected to be charged with murder, sources close to the investigation said.