MCI Communications Corp. said yesterday it had reversed the losses that it suffered in 1986 as cost-cutting, new products and a tapering off of heavy investment spending produced a profit of $88 million (31 cents a share) for 1987.

It said sales rose 10 percent, to $3.9 billion, in 1987 from $3.6 billion a year earlier.

"We were able to cut $300 million out of our capital programs. That makes a significant impact in our profitability and cash flow," Daniel F. Akerson, chief financial officer of the Washington-based telecommunications company, said yesterday.

MCI made money in the first three quarters of 1986, but ended with losses of $448 million for the year as a whole because of a $585 million writedown it took in the final quarter to cover technically outdated portions of its network.

It also began a painful restructuring during that period, laying off about 2,300 employees, or about 15 percent of its work force.

Each of the company's 1987 quarters was profitable, giving MCI 44 consecutive profitable quarters, with the exception of the fourth quarter of 1986.

In the final period of 1987, MCI earned $33 million (11 cents), compared to a loss of $502 million a year earlier.

Revenue in the fourth quarter was just over $1 billion, up 13 percent from $920 million a year earlier.

MCI says that traffic on its network grew by about 25 percent in 1987, about twice the rate of growth of the industry as a whole.