Houston, TX (Sports Network) - Hunter Pence clubbed his second career grand slam, as the Houston Astros edged the Chicago Cubs, 4-2, in the second of a three-game set from Minute Maid Park.

Chris Sampson (3-3) gave up two runs on seven hits in 6 2/3 innings to pick up the win.

Pence finished 3-for-4 at the plate for the Astros, who have two of their last three games.

Ryan Dempster (5-2) allowed four runs on six hits in six innings to absorb the loss.

Aramis Ramirez belted a two-run homer for Chicago, which had won five of six coming in. Derrek Lee went 3-for-4 and scored a run, while Mark DeRosa added a pair of hits.

All six runs were scored in the fourth inning.

Ramirez followed a leadoff double by Lee with his eighth home run of the season, but the Astros pulled ahead in the bottom half.

The first two batters reached base, as Miguel Tejada doubled and Lance Berkman worked a walk. Both runners moved into scoring position when Carlos Lee flied out. Dempster then issued a free pass to Geoff Blum to load the bases for Pence, who tattooed the right-hander's 2-0 offering into the right field seats.

In the seventh, Chicago had the go-ahead run at the plate, but Doug Brocail fanned Alfonso Soriano to end the threat.

Jose Valverde tossed a scoreless to ninth to record his 13th save of the season.