The top management changes announced Tuesday by American President Cos. at two of its principal divisions stem in part from market pressures, company evolution and individual personalities and abilities, said market analysts.

As reported, APC announced that Timothy J. Rhein would replace Don Orris as head of American President Domestic. He was president of American President Lines, and his title will now be president and chief executive of APD.Also at APD, Michael Diaz will become executive vice president and chief operating officer, reporting to Mr. Rhein.

In addition, George Hayashi, APC's vice chairman, will become president and chief executive of APL. John G. Burgess, APL's newly named vice president and chief operating officer, will report to Mr. Hayashi.

Mr. Rhein and Mr. Hayashi both will report to Bruce Seaton, APC's chairman.

Neither Mr. Seaton, Mr. Hayashi, Mr. Rhein nor Mr. Orris were immediately available to comment on the changes.

Analysts said APC has been under increasing earnings pressure, particularly on the domestic side of the business, which has faced growing competition.

In addition to the normal pressure to perform, APC also must contend with being a market leader and all the responsibilities that carries.

Placing Mr. Rhein and Mr. Diaz in APD is seen as a way to shore up this area, analysts said. This is not to say that APL operates in a playground either, analysts said.

"Tim (Rhein) didn't step out of the frying pan into the fire," said Dan Smith, senior analyst with San Francisco-based Manalytics Inc., a consulting company. "He stepped between two fires."

Most people give Mr. Orris high marks for building up the domestic business but believe that at some point, as conditions in the business started to turn down, differences developed in management style.

One consultant said his shoes will not be easy to fill but Mr. Rhein also has the strong support of top management.

Luella Price, an analyst with Donaldson, Lufkin & Jenrette Inc., added: ''The only thing that it appears to be is a difference in philosophy as to how the domestic and the whole company fit together. They just weren't heading in the same direction."

Another official close to the company added that this should not be seen as a panic move to stem financial difficulties. Rather it is part of an industrywide trend toward a seamless organization and the coordination of different services.

There are also likely to be some additional layoffs, the official said. ''There's going to be continued fallout. I can't put a number on it." APC said at its annual meeting that some selective efficiency moves were anticipated.

Some of the key tasks APD faces include cementing its reputation as a premium service, Mr. Smith said. "I don't think they're yet in a position, day in and day out, to establish a premium rate for their service. They're still battling discounters."

Analysts said the move by Mr. Hayashi to head APL may be of relatively short duration. They said he has reduced his role in the company in recent quarters. If, in fact, the move to APL is temporary, another strong leader will be needed. "It's not an easy spot to fill," one analyst said.

Mr. Smith said the move to tap Mr. Rhein made sense because it would be very difficult to find someone outside the company to replace Mr. Orris on short notice.