Jeff Kent and Russell Martin led the way with home runs, and James Loney extended his season-opening hitting streak to 14 games.
Loaiza (1-2) allowed a run and three hits, struck out two and walked none. The right-hander, who made his big league debut with the Pirates in 1995 and has pitched for seven other teams since, is 2-0 in two appearances against them.
"Loaiza's a professional pitcher, and his job is to be prepared whenever he goes out there," Martin said. "That win was his for the taking, and he did a good job of keeping it that way. He really started getting in a groove, painting the outside corner and using his variation of his fastball with his cutter. He executed his game plan to perfection."
Kuo, making his second start this season and the first that he was scheduled to make, threw 75 pitches over four innings. The left-hander allowed a run and two hits, struck out six and walked three - all consecutively.
"We were going to let him go 80-85 (pitches), but once he finished that inning with 75 pitches, that was enough," manager Joe Torre said. "The first inning is what knocked him out of the box. He had 32 pitches that inning. He's intriguing, there's no question about it."
Kuo's first start was April 2, when Torre decided to hold back Chad Billingsley until later in the game because of the threat of inclement weather.
"Kuo was a little erratic at the beginning, but he still battled," Martin said. "He has that fastball that looks invisible to hitters. It seems like he can just throw fastballs all day, and hitters have a hard time making contact. He creates his own damage sometimes by walking people, but if he stays around the zone, he's going to be all right."
A bases-loaded walk to Ronny Paulino in the first gave Pittsburgh the lead, but the Dodgers pulled ahead 3-1 in the fourth on a two-run double by Andre Ethier and Loney's run-scoring single.
Loney is one of two players to hit safely in each of his team's first 14 games this year, along with Pittsburgh's Nate McLouth. Kansas City's Billy Butler had his 13-game streak snapped by the Seattle Mariners earlier Tuesday.
McLouth, whose three-run homer in the ninth off closer Takashi Saito sent the Pirates to a 6-4 win on Monday, kept his streak alive with a first-inning single and hit a broken-bat double in the eighth. He is the first Pirates player to open a season with a 14-game hitting streak since Hall of Famer Willie Stargell in 1976.
Los Angeles extended the lead to 8-1 in the fifth, scoring five runs with two outs. Rafael Furcal hit an RBI single and Matt Kemp followed with a triple that chased Matt Morris (0-2). Paul Dumatrait relieved and plunked Ethier with a 1-2 pitch before Kent drove a 2-1 delivery deep into the left-field pavilion.
"That fifth inning there - two outs, man on second - then all of a sudden they ended up getting five runs," Morris said. "I was one pitch away from getting out of it and keeping it at 3-1. It's just location and how sharp your pitches are. But the location's been off. And seeing more pitches as the game goes on gives them an advantage."
Kent's third homer of the season increased his RBI total to 1,468, vaulting him past Rusty Staub for 50th place. Kent's 368 homers are tied for 65th place on the career list with teammate Andruw Jones, who hasn't hit one since Sept. 19 with Atlanta.
Martin, who led NL catchers last season with 19 homers, led off the eighth with his first of the season. Jones singled and scored on a double-play grounder by Loaiza.
"I'm not really trying to swing for the fences. I'm just trying to hit the ball as hard as I can and stay with my game plan," Martin said. "My game is hitting the ball gap to gap and hitting it where it's pitched. The last couple of games I feel like I've been having better at-bats."
The Dodgers and Pirates were among nine big league teams that dressed all uniformed personnel in No. 42 jerseys to commemorate the 61st anniversary of Jackie Robinson's first game in the majors. Robinson's longtime Brooklyn Dodgers teammate, Don Newcombe, threw out the ceremonial first pitch. He was accompanied by Kathy Robinson Young, Jackie's niece.
Notes: Dodgers broadcaster Vin Scully recalled a game in 1951 at Cincinnati's Crosley Field, where Robinson received pregame death threats. Teammate Gene Hermanski suggested during a pregame clubhouse meeting that all the players wear No. 42, thinking it would confuse any potential assassin.