BB is a super duper laggfish, running 55/26/2 over 60ish hands. MP is one of the better regs in the game, running 21/18/2.9 over a ton of hands. We don't have a lot of history post-flop. My question ldo: is this ever a bluff?

Full Tilt No-Limit Hold'em, $6.00 BB (6 handed) - Full-Tilt Converter Tool from FlopTurnRiver.com

saw flop

Hero (CO) ($1200)
Button ($285.75)
SB ($600.75)
BB ($1579.25)
UTG ($1310)
MP ($1828.25)

Preflop: Hero is CO with A, K
1 fold, MP raises to $24, Hero raises to $81, 2 folds, BB calls $75, MP calls $57

Flop: ($246) 7, 3, 4 (3 players)
BB checks, MP checks, Hero checks

Turn: ($246) K (3 players)
BB checks, MP checks, Hero bets $201, BB calls $201, MP raises to $777, Hero...