Rickey Henderson stole three bases to break his own American League record as Oakland and Seattle split a doubleheader yesterday in Oakland, the A's capturing the nightcap, 8-3, after the Mariners won the first game, 5-2.

Henderson stole his 101st base in the first inning of the opener, snapping the record of 100 he set in 1980. He then stole two more bases in the first inning of the nightcap and now has 103 steals on the season, just 15 behind Lou Brock's major-league mark of 118.

Henderson had asked to rest in the second game, but the unavailability of Dwayne Murphy (out with the flu) forced Manager Billy Martin to deny the request.

"He was tired," Martin said, "but Murphy got sick. I told Henderson if (Seattle pitcher Rich) Bordi stayed in there longer, he'd get four more."

Martin apparently noticed that Bordi, who was with Oakland before going to Seattle, did not have a very good pickoff move. Bordi was knocked out after only a third of an inning, but Henderson stayed in the game until he suffered a cut on the bridge of his nose after running into the wall in the ninth inning.

Henderson's infield single and steals of second and third keyed a three-run first against rookie Bordi (0-2). Henderson singled and, with Dan Meyer batting, stole second and third on consecutive pitches. He scored on Meyer's ground out. Jeff Burroughs followed with his 10th homer for a 2-0 lead and, after Tony Armas singled and Wayne Gross doubled him to third, Bordi was replaced by Bryan Clark. Clark allowed a sacrifice fly by Davey Lopes for the third run.

Steve McCatty (6-1) pitched six innings and gave up just four hits. Dave Beard pitched three innings of one-hit ball for his ninth save.

In the first game, Jim Beattie (7-8) pitched a four-hitter as the Mariners scored all five runs off loser Brian Kingman (2-9).