Winston B. Prude, a former Justice Department lawyer arrested last week after allegedly buying heroin from an undercover police officer, attempted to commit suicide by taking an overdose of the tranquilizer Valium early Monday morning, sources close to the case confirmed.

Prude, 31, called a friend after taking the pills, according to a source. He was placed in the intensive care unit of Capitol Hill Hospital and was transferred yesterday to the psychiatric ward of the Washington Hospital Center.

Sources said Prude, who worked for Justice's Immigration and Naturalization Service until December, was upset about publicity surrounding his arrest May 16 outside a Northeast Holiday Inn with Eric M. Breindel, 27, a Harvard Law School graduate who was a staff member for the Senate Select Committee on Intelligence.

After Breindel's arraignment in U.S. District Court, Sen. Daniel Patrick Moynihan (D-N.Y.), vice chairman of the intelligence committee, asked for and received Breindel's resignation.

Police charged both lawyers with possession of a total of five envelopes of heroin after they allegedly bought the drugs from the undercover officer for $150. In a complaint filed with the court, police said they set up the meeting with the two men after an informant tipped them that they were buying heroin. Both men were released on $5,000 bond.

According to the police complaint, Prude attempted to flee after the officers confronted him outside the motel, but was immediately recaptured by police officers. He appeared at the arraignment before Magistrate Jean E. Dwyer with a black eye.

A native of Amory, Miss., Prude graduated from the University of New Mexico in 1974 and received a law degree from the University of Mississippi in 1978. The following year, he began working for the immigration service as an examiner after he was recommended to the Justice Department by former Sen. James O. Eastland (D-Miss.).

Eastland, who at the time was chairman of the Senate Judiciary Committee, said last week that he knew Prude through his friendship with Prude's grandfather-in-law, a prominent industrialist in Eastland's home state.

"I recommended him," Eastland said. "He's from one of the finest families in the state."

Prude's father, J. O. Prude, a lawyer in Amory, said, "I have the utmost confidence in my son's integrity. I'm a lawyer. My father is a lawyer. I don't think Winston would do anything to violate that tradition."

Citing the fact his client is in the hospital, John Gerstein, Prude's lawyer, has asked for a postponement of a preliminary hearing on the drug charge scheduled for Friday.

No plea has been entered by either man.

Prosecutors said they want to debrief Breindel to make sure no sensitive information was compromised in the two months he worked for the intelligence committee, where he had access to information classified as top secret.

Moynihan has made it clear to the Justice Department that he wants a full investigation to determine if any information was compromised by his former protege, according to sources.

Breindel's attorney, William W. Taylor, said yesterday that "no confidential information was disclosed."