District and Prince George's County officials have kept up a steady drumbeat of good news about the economy in their respective jurisdictions in recent weeks, but muffled sounds of potential problems can be heard in the background.

Interestingly, growth in certain sectors of the economy in both jurisdictions is threatened by pronounced weaknesses in a mass-transportation system that may be further short-circuited by the Reagan administration. It is a good-news, bad-news scenario that deserves a fresh look by the private sector.

First, the good news.

In his state of the economy address last month, Prince George's County Executive Parris Glendening noted that the county began to reach its potential in 1985.

Prince George's County moved past several jurisdictions last year to rank second -- behind Fairfax County -- in the amount of commercial development under construction, Glendening boasted in his remarks.

Indeed, a recent study by the Metropolitan Washington Council of Governments not only supported Glendening's claim, but documented claims that only Prince George's and Arlington counties recorded increases in commercial space in 1985. New nonresidential space in Prince George's County increased nearly 2 million square feet last year, or almost 200 percent, according to COG.

In the meantime, state employment officials recently reported that job growth in Prince George's County exceeded the state average for the fiscal year. The county gained 13,500 jobs in the fiscal year.

In the District, meanwhile, the office of Finance and Revenue recently reported record commercial sales activity for the month of December and a 40 percent increase for all of 1985. Commercial sales in December were $199 million, or almost four times the total that was reported for that month a year earlier, according to the office of Finance and Revenue. Commercial sales for all of 1985 totaled $823 million.

The commercial real-estate sales figures afforded D.C. Mayor Marion Barry yet another opportunity to tout the city's progress in bolstering economic development. "This is one in a series of signs that our efforts to revitalize downtown and other commercial areas are working, and that business people and organizations have realized that it makes sense to locate in the District," the mayor declared.

Now, the bad news.

Glendening referred to it as a major challenge. Left unsaid is the fact that a good deal of the development that has taken place in the county and some of the plans that have been formulated were based on assumptions that the long-awaited Metro Green Line would be completed. The Reagan administration's plans to eliminate funding for Metro construction obviously is cause for much concern among developers and government officials in Prince George's County.

"I guarantee you that Prince George's County, along with the other Washington-area jurisdictions, will be fighting tooth and nail to assure complete funding for the Green Line," Glendening vowed.

In the future, he added: "We may ask the business community to lend its considerable voice to this effort."

Barry, meanwhile, is asking the business community for a different kind of support. The mayor has been traveling to the suburbs in his campaign to get employers outside the District to hire more unemployed D.C. residents.

The unemployment rate in the District, though considerably lower than it was a year ago, is more than twice the rate in surrounding jurisdictions. The problem, however, not only is a scarcity of jobs in the District as it is a lack of adequate, affordable transportation to employment centers in the suburbs. Completion of the Green Line -- placed in limbo in the District by the same protracted political posturing that has stalled completion of the system in Prince George's County -- would eliminate part of the transportation problem.

Realistically, however, even if the entire 103-mile Metrorail system is completed, a proliferation of major employment centers, far removed from planned Metro stations in suburban communities such as Prince George's County, someday will dictate a need for more automobile trips. At the same time, thousands of unemployed D.C. residents will find themselves further isolated from jobs in the suburbs.

The private sector, then, particularly employers in major suburban office and industrial parks may need to do more than give vocal support for the Green Line, as Glendening suggests. Indeed, the private sector should consider transportation alternatives for its own benefit, including joint-venture, privately operated bus systems to ferry workers to employment centers and to augment public transportation.