The chairman of the nonprofit corporation that runs Prince George's County's three public health facilities issued what he termed an "emphatic rebuttal" yesterday to allegations of nepotism, conflicts of interest by board members and other fiscal improprieties.

Francis J. Aluisi, chairman of the Community Hospital and Health Care Systems Inc., responded in a letter to County Executive Parris Glendening, who two weeks ago demanded explanations concerning alleged "irregularities . . . in the management of that organization." The corporation oversees Prince George's General Hospital, the Greater Laurel-Beltsville Hospital and Bowie Health Center.

Earlier this week, Aluisi said, the board created an ad hoc committee of "unimpugned" members to evaluate the allegations. He said the panel had retained a Baltimore lawyer to assist it where necessary.

The allegations involve primarily the propriety of board member and secretary Wayne K. Curry serving as paid general counsel and the employment by the corporation of relatives of board president Robert J. Brady.

The board responded to the allegations by conceding matters of fact, but defending its actions as proper and in the best interests of the facilities.

For example, the board acknowledged the hiring of two sisters and the sister-in-law of Brady, as well as his brother, a professional photographer, but said no favoritism was shown. The women, all nurses, were employed during a nurses' strike in 1983, and one accepted a permanent position at Bowie after the strike was settled.

"That one or more of Mr. Brady's relatives might work or have worked for us is no great surprise considering how many employes there are and, quite frankly, how many Bradys there are," the board said.

Curry's law firm, which has received $204,000 in fees, was selected from among several firms that submitted bids. "We regard his services and those of attorneys in his firm to be satisfactory and economical," the board said, adding that fees charged were "substantially below market rates."

The corporation also defended arrangements with firms that employ board members Roy I. Dabney Jr., an assistant vice president of the First American Bank of Maryland, and Thomas G. Dugan, a vice president of Legg Mason. Both directors, the board said, disclosed their interests and abstained from voting on matters affecting their firms.

The board also disputed allegations that the hospital corporation was inefficient in collecting overdue accounts, had unreasonably delayed hiring a full-time chief executive officer and had bypassed normal political channels in seeking $3 million in renovation funds from the state legislature.

Glendening's letter preceded the corporation board's vote to fire its vice chairman, Sylvester (Fred) Frederick, a Laurel car dealer who, at corporation meetings, had repeatedly questioned board actions. Frederick, who also chaired the separate Laurel-Beltsville hospital board, was ousted Feb. 25 after he went outside the corporation with his ethics complaint against Curry.

Without mentioning Frederick in his response, Aluisi blamed the corporation's problems on "a few corporate directors [who] refused to accept the will of the majority . . . . We are convinced the main objective behind these defamatory remarks is to remove Greater Laurel-Beltsville Hospital from the health care delivery system."

Aluisi said the "accusations and rumors" cited by Glendening included "misstatements of fact, distortions and matters of private concern . . . . "