After more than two years on the sales block, United Press International was acquired today by Media News Corp., a company organized by a group of publishing and broadcast executives specifically to buy the financially troubled wire service from its parent, E.W. Scripps Co.

A UPI story announcing the sale said that Roderick W. Beaton would remain president of the 75-year-old wire service. Media News also said it would retain the UPI name and did not plan changes in the worldwide staff, which numbers about 1,900.

While UPI's Cincinnati-based parent, Scripps, has been a regular money-maker, the news wire reportedly has been unprofitable for about a quarter of a century. UPI lost about $4 million in 1981, but UPI spokesman William K. Adler said the service hopes to cut $1.8 million from that figure in 1982.

Most of the principals were not immediately available for comment.

Reached by phone, Scripps President Edward W. Estlow declined to comment, saying, "The terms are not going to be announced because both companies are private so we don't have to discuss them."

Douglas Ruhe, managing director of the new company, is quoted by UPI as saying: "Media News is acquiring a modern news and information gathering system which is debt free, has a significant positive net worth and adequate capitalization to effect a turnaround."

Ruhe, 38, who has worked for 13 years as a reporter and in television production, is president of Focus Communications in Nashville, which is involved in developing new television delivery systems. The other Media News principals are:

* Len R. Small, 39, editor and publisher of the Moline (Ill.) Daily Dispatch and one-time UPI reporter in London and Paris. He is vice president of the Small Newspaper Group, which has seven dailies and three weeklies in the midwest and California.

* William E. Geissler, 36, a former reporter and editor who is vice president of Focus.

* Cordell J. Overgaard, 48, a Chicago attorney and president of a cable television company.

A number of other organzations considered, then decided against, acquiring UPI, including Reuters Ltd., the London-based international news company.

In March, the ailing New York Daily News, in cost-cutting measure, dropped the wire service. It was a staggering blow for UPI, which collected about $55,000 a month from the Daily News for news-wire and photography services. UPI has continued the service at no charge in hopes that the tabloid will reconsider.

Meanwhile, employes of the Des Moines Register and Tribune Co. were told today that a formal recommendation has been made to cease publication of the afternoon Des Moines Tribune at the end of the summer.

Executive Editor James P. Gannon read a statement that said the recommendation will be considered at a June 21 board meeting.

Gannon said the recommendation came from a special committee formed to study future prospects of the Register and Tribune.

Gannon told employes that between 150 and 200 people would lose their jobs.

Although an afternoon edition may be offered for street sales, the combined paper will be "predominantly" a morning paper.