The Washington Post Co. said yesterday that its profit increased 86 percent in 1987, including a one-time gain of $54.3 million from the sale of the company's minority interests in cellular telephone operations in Washington-Baltimore and Detroit and in four SportsChannel cable television networks.

The Washington-based media company reported net income of $186.7 million ($14.52 a share) for 1987, up from $100.2 million ($7.80) in 1986.

Excluding the nonrecurring gain, the company's 1987 net income was $132.4 million ($10.30), up 32.2 percent from 1986.

Revenue for 1987 was $1.3 billion, up 8 percent over revenue of $1.2 billion in 1986.

For the fourth quarter of 1987, the company earned $64.4 million ($5.01), a gain of 78 percent over income of $36.3 million ($2.82) for the fourth quarter of 1986.

Excluding one-time gains from the sales of operations, 1987 fourth-quarter income was $40.9 million ($3.18), an increase of 13 percent over 1986 fourth-quarter income.

Fourth-quarter revenue was $365 million, up 10 percent over revenue of $333.5 million for the same quarter a year ago.

The company said its newspaper division operating income in 1987 rose 12 percent, to $145.1 million from $130.1 million in 1986. The division's revenue rose 10 percent, to $648.1 million in 1987 from $589.3 million in 1986.

Newsweek magazine's operating income in 1987 was $15.3 million, a decrease of 15 percent from $17.9 million the previous year. Newsweek's revenue totaled $322.2 million in 1987, compared with $320.9 million in 1986.

Operating income for the company's broadcast division was $70.3 million last year, about even with $70 million in 1986. Broadcast revenue increased 3 percent, to $171.4 million from $167.1 million in 1986.

The company's cable division operating income in 1987 was $17.8 million, up 51 percent from $11.8 million in 1986.

Cable division revenue for 1987 totaled $98.6 million, an increase of 16 percent over revenue of $84.9 million in 1986.

UNC Inc., a high-technology services company in Annapolis, said its earnings rose slightly in 1987, to $18.1 million ($1.07) from $17.9 million (99 cents) a year ago.

The company, which has operations in aerospace, telecommunications and defense, said its revenue rose 29 percent during the year, to $495.9 million from $385.7 million.

In the fourth quarter, profit fell 33 percent, to $3.4 million (19 cents) from $5.1 million (32 cents) a year ago, the company said. Revenue in the quarter rose 17 percent, to $128.9 million from $109.7 million.

UNC, which has been going through a major restructuring in recent years, said its earnings from continuing operations were up 20 percent for the year and 26 percent in the fourth quarter.

UNC also said it had discontinued a business under which it had operated the nuclear reactor facility at Hanford, Wash., for the U.S. government. The company said its results for the year did not include $104.2 million in revenue and $7.2 million in profit from its Hanford operations.

Ameribanc Investors Group, the Annandale-based owner of Ameribanc savings bank and a real estate investment company, said its profit increased 6 percent in 1987, to $8.2 million ($1.29) from $7.7 million ($1.26) a year ago.

The company said earnings were hurt by tax reform, which temporarily increased Ameribanc's effective tax rate to 43 percent from 37 percent.

The company had total revenue of $105.7 million during the year, up 15 percent from $91.8 million in 1986.

Ameribanc said its fourth-quarter earnings fell 23 percent, to $1.6 million (25 cents) from $2.1 million (34 cents) a year ago. Revenue in the quarter rose 29 percent, to $30.8 million from $23.9 million.

VM Software Inc., a Reston-based software developer, said its earnings fell 31 percent in 1987, to $3.4 million (53 cents) from $4.9 million (77 cents) a year ago. Revenue rose 13 percent, to $30.6 million from $27 million. In the fourth quarter, VM earned $2.3 million (37 cents), down 6 percent from $2.5 million (39 cents) in last year's fourth quarter. Revenue in the quarter rose 11 percent, to $11.5 million from $10.4 million.