The Reagan administration yesterday sent to Congress a budget proposal for 1987 that would reduce federal funding for the arts and humanities endowments by $32.9 million and virtually eliminate the $21.3 million Institute of Museum Services.

The Reagan budget also would eliminate a $2 million National Capitol Region Arts and Cultural Affairs Program, a new fund established by Congress just last year to help Washington's museums and performing arts groups. A postal subsidy for nonprofit organizations also would disappear under the Reagan proposal, with a 98.5 percent cut that one symphony orchestra lobbyist predicted would have "disastrous" effects on the fund-raising activities of arts institutions.

Not everyone lost yesterday. Under the president's plan, the Smithsonian Institution would receive a funding increase of approximately $15 million, while the federal operating allowance for the John F. Kennedy Center for the Performing Arts would grow by $215,000 and the National Gallery of Art's would increase by approximately $176,000.

This is not the first time that the Reagan administration has sought substantial cuts in the federal endowment budgets, which provide federal subsidies to thousands of scholars, teachers, artists, performing arts groups and institutions around the country. In 1981, Reagan proposed cutting the budgets of the arts and humanities endowments by 50 percent each. Congress restored the cuts and then some. Last year the administration proposed a $30 million reduction in endowment spending and the elimination of the Institute of Museum Services. As has become traditional during the Reagan years, however, opposition from Congress resulted in a compromise that kept endowment funding steady and resurrected the IMS, which the administration been trying to get rid of since 1981. (The institute provides federal operating grants to the nation's museums, zoos and botanical gardens. The Reagan administration would like the private sector to assume that responsibility.)

This year, uncertainty on Capitol Hill over the Gramm-Rudman-Hollings budget-balancing law has made congressional arts patrons less optimistic that funding will be kept level. Gramm-Rudman requires that the federal budget deficit be reduced to $144 billion in fiscal 1987. If it is not, phase two of Gramm-Rudman would require that by Oct. 15, all government programs be cut by a percentage to be determined by the size of the deficit. Phase one of Gramm-Rudman already means that the endowments, like the rest of government, will absorb an automatic 4.3 percent cut to this year's budget by March 1.

*"I don't have any idea this time," said Rep. Sidney R. Yates (D-Ill.), chairman of the House Appropriations subcommittee that has restored cuts to the endowments in previous years. "We don't know how this is going to evolve at all. You have to hear what's going on here. All you hear is Gramm-Rudman, Gramm-Rudman, and 'Do we have a tax increase or not?' It's chaos."

"The proposals are not much different than last time," said Sen. Claiborne Pell (D-R.I.), one of the sponsors of the legislation that created the endowments 20 years ago. "I think (the endowments) have taken a relatively proportionate share of the axe."

* Under the president's proposal, the budget of the National Endowment for the Arts would be reduced by 12.5 percent, from $165.6 million to $144.9 million. Humanities endowment funding would drop by 9.3 percent, from $139.4 million to $126.4 million. The Institute of Museum Services budget would be reduced by 98.5 percent, from $21.3 million to $330,000, or just enough to close down operations.

Arts endowment Chairman Francis S.M. Hodsoll yesterday said the arts budget was exactly what he had requested, and would allow the endowment to continue its programs with little inconvenience. "We think we can work with this budget," he said, adding that the endowment would reduce funding for federal arts programs for cultural institutions like symphony orchestras and opera companies, which traditionally have more access to private philanthropy.

Don Moore, executive director of Dance/U.S.A., a national trade association for dance groups, echoed other lobbyists, saying that he had been so worried about Gramm-Rudman's effects on the budget that the Reagan proposal is almost a relief. "My feeling frankly is that I'm delighted they didn't come any lower," Moore said, adding that he still hopes Congress will find a way to keep arts funding at its present levels.

Museum lobbyists, faced for the fourth time with the proposed demise of the Institute of Museum Services, were less sanguine. "We're going through the same charade that we've gone through for the past four years," said Larry Reger, executive director of the American Association of Museums. "I'm just surprised the administration keeps taking this position. The've just nominated someone (Lois Burke Shepard) to run the agency and now they're proposing to eliminate it. I think the Congress will continue to override the administration."

Rep. Thomas Downey (D-N.Y.), chairman of the 51-member Congressional Arts Caucus, was cautiously optimistic, predicting that Congress would restore the Institute of Museum Services to its 1986 funding levels. "I didn't vote for Gramm-Rudman," he said. "I think it's a dumb idea. The endowments are important programs. They feed America's soul. They do not cost a lot of money, given the total budget."

Amidst all the slashing and cutting, officials at the Smithsonian yesterday expressed quiet satisfaction at their good fortune. Last year, the Reagan administration gave the Smithsonian a 6.5 percent budget increase. This year, its budget would go up by approximately 7.6 percent, from $199.9 million to $215.2 million. Smithsonian Assistant Secretary for Administration John F. Jameson said approximately half of the proposed increase would be used to pay for added communications, salary and utility costs. Another $4.2 million would pay for opening and operating the Quadrangle project on the Mall, which is scheduled to be completed by spring 1987. Another $1.5 million would go to complete the Smithsonian's Museum Support Center in Suitland.

Jameson declined to speculate on the reason for the Smithsonian's conspicuous good fortune except to say that the institution "had presented what OMB regarded as an acceptable proposal."

Now that it has the Reagan budget recommendation in hand, Congress will begin several months of appropriations hearings before attempting to draw up a final version of the 1987 budget some time this fall.