Rep. John W. Jenrette Jr. (D-S.C.) was found guilty late yesterday of conspiracy and bribery charges, making him the second member of the House convicted of crimes in connection with the FBI undercover operation known as Abscam.

The jury verdict, reached after 4 1/2 hours of deliberation in the U.S. District Court here, climaxed a five-week trial in which the government contended that Jenrette and his co-defendant, former Richmond businessman John. R. Stowe, conspired to accept payoffs from fictitious Arab sheiks in exchange for Jenrette's promise to introduce private immigration legislation for them. Both Jenrette, 44, and Stowe, 50, were convicted on all three counts of the conspiracy and bribery charges against them.

When the jury forewoman announced the verdict shortly after 6 p.m., Jenrette cringed and bowed his head. Later, he slumped in his seat at the defense table, struggling to control tears, as each member of the jury was polled on the verdict.

"I'm very much in shock," he said later outside the courthouse. "I love this country. I haven't done anything to sell the office." Clearly stunned that the jury reached its decision just hours after the close of his lengthy trial, Jenrette added, "I'm beginning to wonder about our whole system."

"You know I believe in the judicial system, but I just can't see how all the evidence, if they looked at it, could have been run through," Jenrette said.

"Obviously, the videos were all that counted. That's our system of being tried by our peers. I pray that my being in politics or being a congressman . . . that they weren't out to get a congressman. I would like to think that's not the case because I believe in our country . . . ," Jenrette said.

It was on one of those FBI videotapes, made on Dec. 4, 1979, that the jury of eight women and four men saw and heard Jenrette discuss whether he could produce the private immigration bill for a sheik in return for $100,000. And on that same tape Jenrette told FBI undercover agent Anthony Amoroso, "I've got larceny in my blood. I'd take it in a goddamn minute."

A tape made two days later showed Stowe returning to a house on W Street NW here, a house carefully wired by the FBI, where he picked up $50,000 in a paper bag from Amoroso and said he was on his way to Jenrette's Capitol Hill office. That night, in a taped telephone conversation heard by the jury, Jenrette responded, "Everything's fine" when he was asked by Amoroso if he had received a package from Stowe, who was described by the government as Jenrette's "bagman."

The government presented additional evidence, again captured on FBI video and audio tapes, in which Jenrette discussed getting a personal loan from the Arabs, and suggested that Sen. Strom Thurmond (R-S.C.) would take $125,000 in exchange for private legislation for the phony sheik. Thurmond, the senior senator from Jenrette's home state, testified that he never talked to Jenrette about such a deal and, on the same day outside the courtroom, Thurmond, 77, called Jenrette a "lying skunk."

Jenrette, who testified for more than 11 hours in his own defense, denied that he took any bribe money and said that he only signed a note to hold $10,000 for Stowe. Jenrette said he was suffering from bouts with alcoholism at the time he was dealing with the undercover men, whom he said he came to believe were "mobsters."

Jenrette testified that he was only trying to help his longtime friend Stowe obtain a loan to salvage a munitions plant in Jenrette's district from bankruptcy and thereby save 500 jobs for his constituents. But government prosecutor John Kotelly told the jury that Jenrette saw the loan for the plant as a "cover story" that he would use to explain why he had introduced legislation for the phony sheiks.

Kotelly argued that Jenrette also intended to ask Thurmond to introduce the immigration legislation as a courtesy to a legislative colleague, and that Jenrette planned to pocket the $125,000 for himself.

Kotelly, who prosecuted the case along with Justice Department lawyer Reid Weingarten, declined to comment on the jury verdict.

Jenrette is one of six members of Congress charged with crimes in connection with the FBI's elaborate undercover operation, in which bureau agents, and a key government informant, convicted con man Mel Weinberg, posed as representatives of wealthy, nonexistent Arab sheiks, set up a phony business call Abdul Enterprises headquartered in New York, and then put out the word that they wanted to make big-money deals with people in high government offices.

Last week, the House expelled Rep. Michael (Ozzie) Myers (D-Pa.), who was found guilty in August of bribery and conspiracy for taking $50,000 from an undercover agent in the Abscam sting. It was the first time in the history of the House that a member was expelled because of official corruption.