Tenneco Inc., the energy, chemical, shipbuilding and insurance combine, had a drop in first-quarter per-share profit to $1.51 from $1.61, although net income rose to $194 million from $188 million, the company reported yesterday.

There were more than 12 million more shares outstanding this year than last year, principally because of stock issued last spring in the acquisition of Southwestern Life Corp. Sales rose to $3.8 billion from $3.316 billion.

Chairman James L. Ketelsen told the annual meeting that "despite the recessionary conditions in the world economy [the] first quarter was the best first quarter in our history." Oil operations, shipbuilding, gas pipelines and the packaging division all contributed to the gains, Ketelsen said.

Rockwell International Corp. reported net income in the quarter ended March 31 rose 16 percent to $92.6 million ($1.22 a share), from $79.7 million ($1.08) in the same period last year.

Sales of $1.79 billion were about the same as last year, the company said. For the six-month period, Rockwell's income was $148 million ($1.95), down slightly from $148.4 million ($2.02). Sales rose to $3.4 billion, from $3.3 billion.

Bristol-Myers Co., the cosmetics and pharmaceutical house, earned $1.01 a share in the first quarter, up from 88 cents a year earlier as sales rose 11 percent to $859.7 million from $771.5 million.

Net income rose to $67.25 million from $58.32 million. Chairman Richmond L. Geld said the main factors in the gain were domestic demand for pharmaceutical and nutritional lines.

Delta Air Lines $27.9 million ($1.40 per share) for the three months ended March 31, up 28 percent from the same period a year earlier.

The board of directors declared a quarterly cash dividend of 40 cents per share, payable June 1 to stockholders of record May 7.