Union Pacific Corp. reports a 17.5 percent increase in its third-quarter profit, spurred by record carloadings on its railroad subsidiary.

Net income was $161 million, or $1.61 per share, for the three months ended Sept. 30, up from $137 million, or $1.35 per share, a year earlier.Revenue rose 17.1 percent to $1.85 billion from $1.58 billion during the third quarter of 1989.

Union Pacific Railroad's earnings rose 4 percent to a record $148 million, despite a $17 million increase in fuel prices.

Overall freight traffic gained 7 percent to 1.08 million carloads, the highest for any quarter in the company's history. The railroad had 1.01 million carloads during last year's third quarter.

Coal loadings were up 10 percent; autos, 13 percent; food products, 14 percent; and containers and trailers, 8 percent. Forest products were down 3 percent, the only slippage among major commodities.

Higher crude prices related to the Persian Gulf crisis helped boost earnings 11 percent for Union Pacific Resources, a natural resources subsidiary.

For the year's first nine months, Union Pacific said profits totaled $442 million, or $4.41 a share, up 3.3 percent from $428 million, or $3.98 a share, in 1989.

Revenue for the nine months rose 12.8 percent to $5.36 billion from $4.75 billion.