Dominic F. Antonelli Jr., a slender, gray-haired, publicity-shy millionaire, who is standing trial for bribery, testified yesterday that he had helped arrange loans for D.C. mayoral aide Joseph P. Yeldell because of their long-standing friendship and had never expected any favors in return.

Antonelli, 56, a parking and real estate executive who put their own financial worth at more than $20 million, underwent more than five hours of questioning by defense and prosecution lawyers yesterday in U.S. District Court, speaking calmly and straight forwardly in a mild voice.

Throughout his testimony, Antonelli told the jury that he had always kept his personal friendship with Yeldell separate from his business dealings with the city agency that Yeldell headed - the D.C. Department of Human Resources.

"Mr. Yeldell was my friend and he was in trouble and I wanted to help him," Antonelli said at one point yesterday morning, as he described what had prompted him to help Yeldell obtain a $21,500 loan from Madison National Bank in which Antonelli is a stockholder and director.

Antonelli, who wears darkly tinted glasses because of eye ailments was called by his chief trial attorney. Edward Bennett Williams, as the first witness for the defense in a dramatic move that clearly captured the attention of the jurors, who have often seemed bord by previous testimony about frequently complex leasing and banking transactions. At times, Yeldell sat on the edge of his seat, as his co-defendant testified.

For Antonelli, yesterday's testimony represented his first detailed public response to a controversy that has surrounded him and Yeldell for nearly two years, since the first disclosures about their financial and business relations were published by The Washington Post. Until yesterday, he had steadily refused to comment publicity about the allegations.

Antonelli and Yeldell have been accused of corruptly conspiring to arrange a highly profitable, 20-year DHR lease of a building owned by a partnership controlled by Antonelli. In return for the $5.6 million lease, given Yeldell a $33,000 loan after helping him get the Madison bank loan.

In his testimony yesterday, Antonelli readily acknowledged that he had provided Yeldell with the $33,000 loan and that he had concealed the source of the money by having the loan arranged in the name of a fictitious person. But Antonelli told the jury that he was motivated by feeling of friendship not by corrupt intentions.

"I didn't want him (Yeldell) to know where the money came from, and I didn't want him to feel obligated to me." Antonelli testified. He said he believed that Yeldell had not learned that Antonelli himself was the lender until newspaper accounts about the loan were published "six or seven months" later.

Similarly, Antonelli testified, he did not know that Yeldell's agency, DHR, was considering leasing a two-story office building at 60 Florida Ave. NE at the time when he first began negotiating to buy the property. The Florida Avenue lease is the one cited in the charges on which Antoenlli and yeldell were indicted.

Yeldell's defense lawyer, John A. Shorter Jr., told the jury in an opening statement yesterday morning that he expected Yeldell also to take the witness stand in his own defense. He indicated that Yeldell's principal arguments would parallel Antonelli's.

Shorter asserted that Yeldell was given Antonelli's help in getting the Madison bank loan "long before" the Florida Avenue lease negotiations started. He said that Yeldell "never knew until some six or seven months later." that Antonelli was the source of the $33,000 loan. And he argued that Yeldell "did not know of any interest Mr. Antonelli had in the (Florida Avenue) property" at the time when DHR started considering leasing it.

For the most part, events described in the trial do not in themselves appear to be in dispute. The prosecution, however, has portrayed the pattern of events as proof of a corrupt relationship between Antonelli and Yeldell, while the defense has argued that many of the events were unrelated to one another, and therefore, should not be construed as evidence of wrongdoing.

In his testimony yesterday Antonelli recounted in matter-of-fact detail conversations he said he had had with Yeldell in 1975 and 1976 that have been previously cited by the prosecution as evidence of corruption.

At one meeting in February 1976, Antonelli recalled, Yeldell handed him a "talking paper" that was previously described by the prosecution as a confidential D.C. government report designed to help city negotiators bargain effectively over terms for the Florida Avenue lease.

Antonelli said he immediately told Yeldell that much of the imformation in the report was "incorrect" and that DHR should hire "some experts" to advise it about real estate practices. Antonelli testified that he later arranged an appointment with Yeldell for a real estate specialist, Justin Hinders, who was soon hired by DHR as a consultant to bargain over the Florida Avenue lease.

Antonelli also described a meeting in Yeldell's office on Dec. 22, 1975, in which Yeldell, according to Antonelli and other witnesses, initiated direct negotiations between DHR and Antonelli over the Florida Avenue building. The meeting occurred ont he first business day after DHR was granted independent powers to lease privately owned buildings.

Antonelli left unclear, however what had prompted the meeting. He said he had received a telephone message at his office on Dec. 19, 1975 - a Friday and the day when DHR's leasing powers were authorized - asking him to come to Yeldell's office on Dec. 22, the following Monday. Antonelli said he did not know who had left the message for him, and he added that he went to the meeting without any notion about why Yeldell wanted to see him.

At several points in his testimony, Antonelli, who is expected to return to the witness stand Monday, either said he could not recall or appeared to contradict descriptions of events given by previous witnesses.

Antonelli testified that he had told Lawrence A. Sinclitico, a title insurance company employe who helped arrange the $33,000 loan for Yeldell, that he wanted the note, or lending instrument, to be "negotiable" - a key factor in determining the maximum legally permissible interest rate in the District of Columbia. Sinclitico, a long-time friend of Antonelli, had previously testified that he never discussed the note's negotiability with Antonelli and that he had simply set the interest rate at 8 percent at Antonelli's request.

During the first part of his cross-examination of Antonelli, Assistant U.S. Attorney Richard L. Beizer appeared to raise doubt about Antonelli's assertion that he had not negotiated directly with Yeldell over [WORD ILLEGIBLE] before DHR obtained its own leasing authority. Beizer produced a Sept. 22 1975 letter from Antonelli to Yeldell that dealt with a city lease for another building owned by Antonelli.

"It was a misdirected letter," Antonelli responded.

During his testimony, Antonelli was repeatedly asked by his chief defense lawyer, Williams, whether he had ever expected any favors from Yeldell, ever bribed Yeldell or even engaged in any corrupt relationship with Yeldell. To each question, Antonelli responded by saying, "No," "No, sir," or "No, I did not."