The Supreme Court, acting at the urging of the Reagan administration, yesterday agreed for the first time to review a key portion of the Voting Rights Act that gives minorities the right to challenge election results that do not reflect their numbers on the voting rolls.

The justices, in a case involving seven state House and Senate districts in North Carolina, agreed to hear North Carolina's arguments that a lower court misinterpreted 1982 amendments to the 1965 law.

The state, joined by U.S. Solicitor General Rex E. Lee, asked the justices to determine whether the law actually guarantees "safe" seats to minorities. The court also agreed to consider how lower-court judges should define racial bloc voting, a necessary factor in triggering the act's provisions. Civil rights advocates worried yesterday that the court may use the case to narrow significantly what they thought they won when Congress passed the 1982 law.

"We are very concerned that the Reagan appointees in the Justice Department, all of whom opposed the amendment, may seize this opportunity to try to persuade the court to gut the Voting Rights Act," said Lani Guinier, an attorney with the NAACP Legal Defense and Educational Fund Inc.

The department argued that the North Carolina court misread the 1982 law to require "guaranteed electoral success in proportion to the black percentage of the population." The case, to be argued next fall, is Thornburg v. Gingles.

The justices, without comment, declined yesterday to hear an appeal by former labor secretary Raymond J. Donovan, who argued that a special federal court improperly gave New York prosecutors federal grand jury documents that apparently were later used to indict him on grand larceny and fraud charges. Donovan has denied the charges.

The documents were developed during a related 1982 investigation by special prosecutor Leon Silverman into allegations that Donovan had ties to organized crime. Silverman concluded there was "insufficient credible evidence" to warrant prosecution.

Prosecutors for Bronx District Attorney Mario Merola obtained the federal documents and testimony from the special federal court. Donovan, who resigned March 15, was indicted in September in connection with a $186 million New York subway project.

In other action, the court:

* Let stand a ruling last year by a federal appeals court that San Jose, Calif., public school officials unlawfully discriminated against Hispanic students and must act to desegregate the system. The court declined to upset the ruling by the 9th U.S. Circuit Court of Appeals in San Jose Unified School District v. Diaz.

* Decided unanimously that the federal Education of the Handicapped Act may require public school officials to reimburse private school costs for parents who on their own decide to transfer a handicapped child to a private school.

Justice William H. Rehnquist, writing for the court, said public schools must pay if courts later determine that the parents were correct. But "parents [who] act without the consent of state or local officials do so at their own financial risk," Rehnquist said. If courts later decide that school officials were right, he said, parents could not be reimbursed. The case is Burlington School Committee v. Massachusetts Department of Education.