Planning Research Corp. cut its interest expenses by half a million dollars this past quarter, allowing the firm to post record earnings, while its revenues slipped by $1 million.

McLean-based PRC, a computer systems and software company, had profits of $2.1 million (30 cents a share) in its first quarter compared with $1.9 million (27 cents) last year. First-quarter revenues declined to $78 million from $79.1 million.

"The company was able to improve its earnings, despite the slight decline in revenue, by cutting its net interest expense by more than $500,000 from the first quarter a year ago," said John M. Toups, chairman and president.

Baltimore-based Crown Central Petroleum came back in its third quarter from losses a year ago of $5.2 million to post earnings of $8.4 million ($1.16). Revenues increased to $466.3 million from $318.8 million. The earnings include a $3.8 million insurance benefit.

For nine months, Crown Central earned $2.4 million (23 cents) compared with a loss of $11.5 million last year. Year-to-date figures include a $6 million loss for the first half. Revenues so far this year are $1.3 billion, compared with $1.1 billion last year. Company officials attributed the improvement to better profit margines, increased sales volume and operating at plant capacity.

Radiation Systems Inc., a high technology antenna-maker based in Sterling, Va., had record first-quarter profits of $652,000 (22 cents), compared with $470,000 (17 cents) last year. Sales increased to $4 million from $2.6 million last year.

Washington Gas Light Co. reported 12-month profits of $20.2 million ($3.30), compared with $18.6 million ($3.38) last year. More shares were outstanding during the latest reporting period. Revenues for the 12 months increased to $670.8 million from $521 million.

Springfield-based Bowl America Inc. posted a first-quarter loss of $31,893, compared with a loss of $30,761. Revenues fell to $3.06 million from $3.15 million. The summer quarter is traditionally a slack period for the firm, company officials said.

Owens & Minor Inc., a Richmond health-care products company, posted profits of $629,870 (33 cents) on revenues of $56 million, compared with $661,411 (35 cents) on revenues of $51.1 million last year. The year-ago figures included a nonrecurring gain. For nine months, Owens & Minor had earnings of $1.6 million (82 cents), compared with $1.7 million (89 cents). Revenues increased to $154.7 million from $131.9 million. The company's stock will split two for one today for shareholders of record Oct. 14. The per-share information is based on that split.

Monumental Corp., a Baltimore-based insurer, posted third-quarter earnings of $2.8 million (40 cents), compared with $4.5 million (67 cents) last year. Premium income in the quarter increased from $31.8 million to $36.9 million.