Washington Real Estate Investment Trust last week sold the Washington Circle Inn at 2430 Pennsylvania Ave. NW for an $11.75 million profit.

The building was purchased by a partnership of RJS Development Co., a Houston hotel group owner, and Muben Realty Co., a subsidiary of Mutual Benefit Life Insurance Co. of Newark, for $14.65 million.

Trust President B. Franklin Kahn said the sale price was nearly $12 million more than Washington Real Estate Investment Trust--known by its stock symbol, WRIT--paid for the building in the late 1960s.

Built in the early '60s as apartments, the building was converted to offices to escape rent control a few years later. Rents jumped again when the offices were turned into luxury hotel suites similar to the nearby Guest Quarters. The new owners plan to continue the building as a suite hotel.

Kahn said that under the owner-financing arrangement, WRIT got the $2.65 million it had invested in the building back in cash and took back a multimillion-dollar mortgage from the buyers. The financing package will increase the trust's annual earnings from the property by 87 percent, he added.

The building had been carried on WRIT's records at its book value of $2.65 million; the sale enabled WRIT to cash in the years of appreciation that didn't show on the firm's balance sheet, Kahn noted.

Other recent developments in commercial realty in the Washington metropolitan area:

* General Electric Co. will be relocating its Washington headquarters offices to the new National Place office, retail and hotel complex at 1331 Pennsylvania Ave. NW. GE, formerly located at 777 14th St. NW, has signed a 10-year lease for 53,000 square feet of space at the complex with occupancy expected in October 1983. The aggregate rental value of GE's lease is about $13 million. National Place is being developed by the Quadrangle Development Corp.

* Solarex Ventures Group has leased 5,600 square feet of space at the Avenel Business Park in Gaithersburg for a solar cell assembly laboratory and administrative offices. The aggregate rental value of the 3 1/2-year lease is $216,000.

* The Council of State Chambers of Commerce is relocating from 499 South Capitol St. SW and has leased 3,345 square feet of space at 122 C St. NW. The aggregate rental value of the three-year lease is $176,000.

* Wilson, Elser, Edelman & Dicker, a New York-based law firm, has leased about 4,500 square feet of space at 600 Maryland Ave. SW. The aggregate rental value of the lease is near $1 million.

Barton-Aschman Associates Inc., a national consulting firm, has leased about 7,000 square feet of space at 1400 K St. NW. The aggregate rental value of the lease is about $1.5 million. CAPTION: Picture, Washington Cicle Inn sold for $14.65 million.