Law enforcement officials yesterday announced the arrest of 19 persons who police said were part of two major drug rings specializing in the distribution of heroin and cocaine throughout the Washington area.

The mass arrests included persons from the District, Maryland and Virginia.

Although they declined to say how much heroin was purchased, officials from the D.C. police norcotics branch and the Drug Enforcement Administration indicated that the persons arrested were wholesalers rather than small time drug dealers. To emphasize this, they noted that some pure heroin was purchased during the six-month investigation. Ordinarily, only wholesalers handle pure heroin, which they later cut for street sale by smaller dealers.

"We have some very important folks," said David Canady, special agent in charge of the Washington office of DEA. He said he expects the arrests "will make an impact on the availability of heroin" in the Washington area.

Canady said the analysis of the heroin purchased showed that the heroin had come from the "Golden Crescent" of Iran, Afghanistan and Pakistan, the world's largest opium-producing area. Officials have been troubled by the increase in the amount of drugs coming into the United States from the Golden Crescent recently.

Earlier this year, three persons were arrested after police seized seven pounds of uncut heroin with a street value estimated at $32 million that officials said had been smuggled directly from an Iranian heroin processing plant.

D.C. Police Lt. William Merritt, who directed the investigation, said police seized 25 ounces of cocaine, valued at more than $50,000, six cars and $5,000 in cash during the arrest of the 19 persons.

Ten of those arrested were named in indictments handed down in U.S. District Court in Baltimore. Sixteen others were named in arrest warrants filed in federal magistrate court in Hyattsville. Seven other persons are still at large.

Among those arrested were Coleman McGowan, a 49-year-old dentist who lives in Rockville. He is charged with conspirarcy to distribute cocaine and distribution of cocaine, according to the indictment.

McGowan allegedly conspired with Vernita Morris, 26, of the same address, to distribute cocaine, according to the indictment.

Most of the offenses occurred in Maryland, although several took place in the District, Virginia and Pennsylvania, according to the indictments.

Others charged in the conspiracy are John C. Anderson, 41, of 3608 St. Johns Place, Landover; Horce O. Jerry, age unknown, of 701 Quarry Ave., Seat Pleasant; Leroy Wells, 25, of 1656 W St. SE, Russell H. Waddell, 28, of 1907 Good Hope Rd. SE; Margo L. Weaver, 39, 616 Raleigh Pl. SE; Joyce Norwod, 23, of 6703 Hasting Dr., Silver Spring; Willie Ross, 43, of 7404 Walker Mill Rd., Seat Pleasant; and Jerry Hairston, 34, of 418 Elm St. NW.

The arrests also include Keith Corbitt, 27, of 9009 Ardmore Rd., Landover; Melvin L. Hudson, 35, of 6833 Eastern Ave., Takoma Park; Sherman Mallory, 32, of 1414 Saratoga Ave. NE, Larry Wider, 31, of 1930 New Hampshire ave. NW; Harold Brown, 30, of 1234 Massachusetts Ave. NW; Reggie Lyons, age unknown, of 4850 Connecticut Ave. NW; Willie Royster, age unknown, of 6038 Richmond Hwy., south of Alexandria; and Joe Payton, age and address unknown.

D.C. Police Chief Burtel M. Jefferson said yesterday's arrests stemmed from a combined investigation by the marcotics branch of the D.C. police force and DEA.