The objective of this study was to determine the relationship between pH decline, [mu]-calpain autolysis, proteolysis of the costameric protein vinculin, and degradation of membrane proteins involved in calcium homeostasis. Commercial hybrid pigs (n=309) from two different genetic lines (lines 2 and 3) were harvested. Longissimus dorsi (LD) pH measurements were taken at 45 min, 3, 6, and 24 h postmortem (PM). In order to obtain animals with variability in pH measurements, two groups (high and low pH at 3 h PM) were selected within each line. Percent drip loss after 24, 48, and 96 h storage was determined. Ten animals were selected within each group to determine autolysis of [mu]-calpain and extent of proteolysis of the ryanodine receptor (RyR1), sarcoplasmic reticulum Ca2+-ATPase (SERCA2), and vinculin at 1 d, 48, 72, and 120 h PM. The line 2/high pH group had a higher (P<0.05) pH than all other groups at 24 h PM and the least (P<0.05) drip after 96 h storage. The line 3/low pH group had the highest (P<0.05) L* value than all other groups. At 1 d postmortem, the high pH groups had increased (P<0.05) [mu]-calpain autolysis compared to the low groups. Increased autolysis of [mu]-calpain was correlated (P<0.05) to higher pH and decreased drip. Line 3 had more (P<0.05) RyR1 degradation (band 2) than line 2 at 48 h PM. An increase in RyR1 degradation (band 2) was related to lower 6 h (P<0.05) and 24 h (P<0.01) pH and increased drip loss at all times measured (P<0.01). Increased proteolysis of intact RyR1 at 1 d and 48 h was correlated (P<0.01) to increased [mu]-calpain autolysis. Increased proteolysis of SERCA2 was correlated (P<0.05) with lower pH and increased drip loss. Decreased degradation (P<0.05) of vinculin was found in line 2/low pH compared to both line 3 groups. These results show that [mu]-calpain autolysis and proteolysis may be related to Ca2+ regulation and may affect pork quality attributes such as water-holding capacity.