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CREDIT MARKETS - NYTimes.com

Interest rates rose slightly yesterday in a very quiet day, with most of the increase coming in the last hour or so of trading. Low trading volume and a narrow range for prices were good signs, dealers said, that the uncertain interest rate outlook had caused many speculators and investors to curb their activity while waiting for more information about the economy.

By late in the day, three- and six-month Treasury bill rates had increased about an eighth of a percentage point, to 12.85 percent and 12.9 percent, respectively.

In the Treasury note and bond market, prices of most issues fell slightly, with new 14 percent notes due in 1986 falling to 99 19/32 to yield 14.13 percent, compared with an average price slightly more than 99 27/32 at Wednsesday's auction.

The seven-year Treasury notes to be sold next Wednesday were offered by dealers on a when-issued basis to yield 14.03 percent. In the 10- and 30-year maturity area, corporate issues must offer higher yields than the 13.93 percent yield on 10-year Treasury notes and 13.48 percent for 14 percent Treasury bonds due 2011 that were offered at 103 22/32. Corporations Discouraged

Many corporations that want to sell notes and bonds are discouraged by high interest rates that start in the mid-teens for high quality companies and rise to more than 18 percent for Baa-rated utilities. Some have turned to the tax-exempt bond market where they may sell bonds at lower interest rates through special authorities created by local governments. Those issues carry lower yields because their interest payments are exempt from Federal income tax.

One recent example of this practice is the Aa/AA+-rated General Motors Corporation, which is financing pollution control equipment at facilities in Michigan through the sale of $87 million of bonds by the Michigan Job Development Authority. The 10 1/4 percent bonds due 2002 are tentatively priced by the First Boston Corporation at 100. The interest rate would have been significantly higher, except that bond holders have the one-time option on March 1, 1985, of redeeming the securities at a price of 100.

Elsewhere in the tax-exempt market, the Metropolitan Sanitary District of Greater Chicago rejected both bids it received for a $60 million issue of Aa-rated revenue bonds. Two groups led by Chicago banks bid for the issue, but in order to keep the interest cost to the authority below the legal maximum of 11.55 percent, they were forced to reduce the maturities from the 1984-1998 range proposed by the district to as near as 1984-1989.

A companion $51 million issue of 9.7 percent notes due in April and November 1983 was won by the Continental Illinois National Bank, but was not publicly reoffered.

In the agency sector, the Federal Home Loan Mortgage Corporation sold $42.7 million of mortgage participation certificates at an average yield of 15.59 percent.

Summary:

assistant: Interest Rates Climb Slightly   Interest rates rose slightly yesterday in a very quiet day, with most of the increase coming in the last hour or so of trading.  Low trading volume and a narrow range for prices were good signs, dealers said, that the uncertain interest rate outlook had caused many speculators and investors to curb their activity while waiting for more information about the economy.   By late in the day, three- and six-month Treasury bill rates had increased about an eighth of a percentage point, to 12.85 percent and 12.9 percent, respectively.