Three major trends have dominated the growing metropolitan Washington economy in the past decade.

The most obvious has been the proliferation of national corporation and trade association offices here, aided by growing employment in such professional support sectors as accounting, law and consulting. This trend reflects the increased decision-making role of government in the private economy.

A second factor -- and one certain to be a dominant force in the 1980s -- is an increase in international business and financial activities. Today's edition of Washington Business focuses on a significant factor in this development, the role of the World Bank and International Monetary Fund, two of half a dozen major international financial institutions based here.

Less recognized is a third trend, the emergence of the D.C. area and the broader Washington-Baltimore market as a major center for scientific research, high-technology design and manufacturing, and communications technology.

Washington long has been a center for research laboratories and small manufacturing firms engaged in technology, with much of the work related to defense. But the growth of the overall private business sector, the attractive labor market of skilled professionals and the drawing power of Washington as the center for economic decision-making are likely to result in an explosion of the technology industry here.

Two regional brokerage companies are paying attention to this sector, one in a pair of presentations open to the general public and the other in a seminar for institutional clients that apparently is the first of its kind.

Ferris & Co. held the first of its two public sessions on local high-technology companies last week and will conclude with another presentation today. Executives of Communications Satellite Corp., Penril Corp., MCI Communications and Flow General spoke last week. Today's session features Atlantic Research Corp., Fairchild Industries, Scope Inc. and Biospherics Inc., from 4 to 6:45 p.m. at the National Housing Center, 15th and M Streets NW.

Alex. Brown & Sons, meanwhile, will sponsor a computer services seminar at the Cross Keys Inn in Baltimore, on Thursday and Friday, with presentations on 20 firms including two based in the Washington area: American Management Systems and STSC Inc.

Speaking to the opening Ferris audience last week, Comsat President Joseph Charyk stated that the 1980s have been heralded as a "world information decade," and he said the driving force will be changes in technology. "We will see a direct challenge to America's greatest traditional strength, its worldwide reputation for technological innovation," he added.

As a firm based here since it was started in 1963, Comsat's people have been in a position to watch telecommunications and other high-technology firms come to this area, he added. Comsat alone employs 1,600 persons locally with an annual payroll of $40 million.

Although Comsat's business in the past has been primarily in the field of international satellite communications services, this Washington business is aiming at a key business market of the coming decade through Satellite Business Systems, a joint venture with insurance giant Aetna and computer giant IBM.

SBS, also based here, will grow large among area enterprises. It plans to launch its first satellite within a couple of months and start commercial operations early next year, allowing large customers new capabilities to communicate a complete spectrum of voice, data, facsimile and televised conferences.

Comsat also is aiming to enter direct-to-home broadcasting services -- which Charyk called a "premium" pay-television concept -- in three years. And the firm is seeking to introduce satellite communications into the environmental information services field.

Although Comsat is the largest of the corporations being highlighted by the brokerage presentations, all of the companies face business expansion in diverse product or service lines. Penril President Kenneth Miller said last week, for example, that a recent sale of 635,000 shares provided management with more than $8 million to "ferret out investment opportunities in the general market areas of high-technology electronic data communications and scientific electronic instruments." He said he would be disappointed if another acquisition isn't made before the current fiscal year ends next July 31.