WASHINGTON -- In the latest sign that the recession may be ending, corporate profits in the first quarter of 1991 fell markedly less than in the two preceding quarters, the Commerce Department said yesterday.

The decline, to an annual rate of $288 billion, was just 0.3 percent. Profits had fallen 1.9 percent and 3.9 percent, respectively, last summer and autumn.

"We are getting a clear moderation," observed Michael P. Niemira, an economist at Mitsubishi Bank in New York. Referring to the recession, he added, "maybe the worst is behind us."

While corporate profits have historically reached their low point at the end of recessions, they represent a coincident rather than a predictive indicator, and analysts were unwilling to cite the report as hard proof of an imminent recovery.

A second gauge, cash flow from current production -- the internal funds available for investment -- climbed 3.8 percent in the first quarter. That compared with a 0.9 percent increase in the fourth quarter of last year and a 2 percent decline in the third.

Yesterday's Commerce Department report also showed that the gross national product fell at a 2.6 percent seasonally adjusted annual pace in the first quarter, a slightly smaller decline than the 2.8 percent initially estimated in late April.

Earlier signs that the nation may be coming out of the recession that began in July have included recent steadiness in housing, retail sales and industrial production, and an upturn in durable-goods orders. Tomorrow, the government will release its Index of Leading Economic Indicators, which is expected to show its third straight monthly advance.

The revision in the GNP, which was in line with expectations, mainly reflected a bigger jump in net exports, by $4.2 billion. That increase was partly offset by a $3.1 billion downward adjustment in output of producers' durable equipment.

The GNP represents the total value of goods and services generated in an economy.