The Washington Post Co. yesterday reported strong first-quarter gains in both revenue and profits with net income, excluding one-time gains, up 53 percent from the first quarter last year.

Net income in the first quarter of 1985, excluding one-time gains, was $13.9 million. Net income, including one-time gains from the sale of part of its SportsChannel and cellular telephone operations, was $24.9 million ($1.78 a share), an increase of 175 percent over net income of $9.1 million (64 cents) in the first quarter last year.

Revenue for the 1985 first quarter was $243.6 million versus $219.5 million last year.

The company said newspaper division revenue in the first quarter increased 10 percent over last year. The Washington Post's advertising inches increased 5 percent overall, bolstered by classified advertising, which was up 11 percent.

Television station revenue was up 15 percent in the first quarter while Newsweek revenue was down 3 percent. The company said there were 12 issues of Newsweek in 1985's first quarter, with 550 pages of advertising, versus 13 issues with 621 pages in the same period last year.

The company said lower SportsChannel losses and better results from Bowater Mersey Paper enabled it to reduce its losses in earnings of affiliates from $4.4 million in the first quarter last year to $148,000 in 1985's first quarter.