PS Business Parks Inc. said net income allocable to shareholders declined sharply in the first quarter ended March 31 due to a decrease in the gain on the sale of real estate. The Glendale-based real estate investment trust reported net income of $5.1 million or $0.23 per diluted share, compared with $7.3 million or $0.33 per share in the same period last year. Revenues were relatively flat increasing $5 million to $58.9 million in the first quarter due to improved occupancy in its portfolio and a $1.8 million payment received from a former tenant in connection with a bankruptcy settlement, the company said.