The profits of American corporations dipped visibly last quarter, the government reported yesterday, reflecting both the recent sharp falloff in auto sales and the start of the current economic downturn.

Commerce Department figures showed corporate profits after taxes down 2.4 percent between April and June, partly offsetting a 7.3 percent gain posted in the previous quarter. Before-tax profits fell 2.7 percent.

At the same time, the department reported that the "real" gross national product, the broadest measure of the economy's output, fell at a 2.4 percent annual rate in the second quarter rather than the 3.3 percent estimated previously.

Officials also revised their estimate of the inflation rate for the April-June period. The department placed the GNP price index at an annual rate of 9.2 percent for the period instead of 9.9 percent as reported before.

Meanwhile, the Federal Reserve Board disclosed that its policymaking Open Market Committee voted 10 to 1 at a special meeting July 27 to push short-term interest rates up further to slow a rapid increase in the money supply.

Minutes of the meeting, published yesterday, showed the panel decided to boost the key federal funds rate -- the interest charged on overnight loans among banks -- to between 10.5 percent and 10.75 percent, from 9.75-10.5 percent before.

The minutes did not reflect decisions taken at last Tuesday's meeting of the panel, held just before the Fed announced another sharp increase in the discount rate, to a record 10.5 percent, also to help fight inflation.

Minutes of the Open Market Committee are held several weeks before being made public. The discount rate, the interest the Fed charges on loans to member banks, is the most visible signal of money and credit policy shifts.

The Fed also reported yesterday that the nation's factories operated at 85.6 percent of their capacity last month, down slightly from the revised June rate. In March, the index was at 87.1 percent, its highest in five years.

The combination of figures provided little new insight into the state of the economy. Most analysts believe the economy has entered a recession which so far still is mild but which may deepen later this year.

The decline in corporate profits was concentrated primarily in the auto industry, which has suffered from a falloff of sales in the wake of the gasoline lines earlier this year and the steep jump in fuel prices.

However, the picture in other industries was generally not too bright. The major exceptions were in food and petroleum industries, where profits rose sharply. Profits in the chemical industry turned down.

Both the profits and GNP figures reflected continuing increases in inventory accumulation -- a development economists regard as worrisome because it could spark a deeper recession.

Profits received from current production -- a measure that adjusts for inventories and other factors -- fell 1.9 percent over the quarter, following a 3.2 percent plunge in the first three months of the year.

The revision in "real" GNP also reflected further inventory building. Real final sales, the broadest measure of buying activity in the economy, fell at a 4.1 percent annual rate.

The figures on profits brought after-tax profits to a new annual rate of $138.6 billion, down from $142 billion in the previous quarter. Before-tax profits fell to a $226.9 billion rate, from $233.3 billion before.

In the July 27 action of the Open Market Committee, both Paul A. Volcker, the Fed's new chairman, and his predecessor, G. William Miller, now Secretary of the Treasury, supported the interest-rate rise.

The lone dissenter on the panel was Nancy H. Teeters,a member of the Fed's board of governors. Volcker was chairman of the New York Federal Reserve Bank when the meeting took place.

Separately, the board announced that Peter D. Sternlight, 51, will become the committee's manager for domestic operations, while Alan R. Holmes, 59, who has been manager of the open market account, will become adviser to the FOMC.