A U.S. District Court jury yesterday heard a taped telephone conversation in which Richmond, S.C., businessman John R. Stowe said Rep. John W. Jenrette Jr. (D-S.C.) was "worried to death" that his conversations with agents for an Arab sheik might be intercepted by federal wiretaps, particularly by the Internal Revenue Service.

That conversation, tape-recorded Dec. 11, 1979, was introduced by government prosecutors yesterday as convicted con man and FBI informant Melvin Weinberg began his testimony in federal court as a key figure in the FBI undercover operation known as Abscam. Jenrette and Stowe are co-defendants in the case on charges that they conspired to get money from the fictitious Arabs in exchange for Jenrette's promise to introduce private immigration legislation.

Weinberg assured Stowe in the conversation that Jenrette "wouldn't be a congressman this long if . . . he wasn't careful, all right?"

Stowe responded, with a laugh, "Well, that's for damn sure."

According to videotaped evidence already shown to the jury, Jenrette and Stowe met at a house on W Street NW, on Dec. 4, 1979, to discuss the deal with Weinberg and FBI undercover agent Anthony Amoroso, who called himself Tony DeVito and said he was the sheik's representative. Two days after, Stowe returned to the house and picked up $50,000 in cash he said he was taking to Jenrette's office, according to another tape recording.

The jury yesterday heard Stowe tell Weinberg that he had received $10,000 of that money from Jenrette. Weinberg tried to set aside Stowe's concern during that conversation, advising him that "the only dangerous part was the time you took the money and left."

"Yeah, I could just see me having a car wreck and the money just flying all over town," Stowe responded on the tape.

Weinberg is expected to continue his testimony for the government today. Meanwhile, defense lawyers yesterday completed their cross-examination of FBI agent Amoroso.

Their questions were focused on defense contentions that Amoroso allowed Weinberg to operate unsupervised, that Weinberg selectively taped conversations and that one critical tape conversation that took place in a barroom is virtually inaudible because of background noise from a football game.

Stowe's lawyer, Murray Janus, yesterday questioned Amoroso about a 200 percent raise -- "from $1,000 to $3,000 a month -- that Amoroso recommended for Weinberg after their first meeting in January 1979. Amoroso agreed with Janus that the raise was meant to keep Weinberg financially satisfied and to discourage any efforts at "hustling on the side" that Weinberg might consider during the Abscam sting.

In a related development yesterday, Judge John Garrett Penn said he will conduct a hearing today on a subpoena issued by the House Committee on Standards of Official Conduct for all of the government's audio and video tapes that have been introduced as evidence into the Jenrette case. U.S. Attorney Charles F. C. Ruff told Penn yesterday that the government wanted the court's permission to comply with the request.