Tenneco Inc. reported first-quarter earnings of $110.1 million yesterday compared with $105.2 million last year.

Earnings were equivalent to $1.10 a share both years but the number of outstanding shares increased from 91.4 million to 95.1 million during the year.

Operating revenues were $2.04 billion, up from $1.83 billion a year earlier.

Chairman Wilton Scott told the annual stockholders meeting all eight of the company's operating divisions were profitable in the first quarter but that integrated oil, natural gas pipelines, automotive, chemicals, and agriculture land management reported higher profits than in 1977.

Curtiss-Wright Co., which is waging a proxy fight to capture control of Kennecott Copper Corp. at Kennecott's annual meeting Tuesday, reported sharply lower earnings and sales for the first quarter yesterday.

Net income was $3.35 million (39 cents a share) on sales of $70.46 million compared with $4.36 million (51 cents) a year earlier on sales $82.34 million.

Chairman T. Roland Berner said an eight-week work stoppage at the company's Wood-Ridge, N.J., plant was a prime cause of the decline.

Aetna Life & Casualty Co. reported operating earnings of $104.1 million for the first quarter of 1978, up from $81.4 million from a year ago.

The company said the earnings amounted to $1.93 a common share compared with $1.51 for the same period in 1977.

Revenues rose 19 percent in the first quarter to $2.4 billion. Premium income was up 18 percent to $2 billion and investment income was up 25 percent to $380 million, the company reported.

Aeta's net income in the first quarter was $97.3 million ($1.80 a share), reflecting realized capital losses of $7.6 million and a tax credit of $782,000. During the same quarter last year, net income was $81.2 million ($1.51).

The company's assets as of March 31 were $21.7 billion, up 19 percent from a year ago. Shareholders equity was $39.04 per common share compared with $32.95 a year ago.