Ca2+ ATPase in Dutch warmblood foals compared with Na+, K+ ATPase: intermuscular differences and the effect of exercise.

The paper investigates how exercise, with or without a subsequent period of grazing in the pasture, impacts the concentration of Ca2+ ATPase in the muscles of Dutch Warmblood foals. The researchers found that Ca2+ ATPase levels were not affected by exercise or rest, a contrast from the results with Na+, K+ ATPase concentration which increased post-exercise.

Research Design and Participants

• The study began when the foals were 7 days old. A total of 24 Dutch Warmblood foals were divided into three different groups: those that stayed in stalls (Box), those that stayed in stalls but also had an exercise routine (Exercise), and those that were left to graze in the pasture (Pasture).
• Half of the foals in each group were killed after 5 months, while the remaining ones were allowed to graze in the pasture until they reached 11 months.

Data Collection and Analysis

• The concentration of Ca2+ ATPase was assessed in muscle homogenates as Ca2+-dependent steady-state phosphorylation from [gamma-32P]ATP.
• The foals’ gluteus medius and semitendinosus muscles (both mixed fibre type), as well as the slow masseter muscle, were examined in the study.
• The results indicated that, regardless of exercise or box rest, the concentration of Ca2+ ATPase remained stable.

Contrasting Results with Na+, K+ ATPase

• Unlike the Ca2+ ATPase, the Na+, K+ ATPase showed a 20% increase in concentration post-exercise in the gluteus medius and semitendinosus muscles.
• There was no significant difference between the three muscles’ Na+, K+ ATPase concentrations.

Key Findings

• The study concluded that Ca2+ ATPase concentration in foal muscle is approximately six times higher in mixed fibers than in slow fibers.
• Unaffected by sprint exercise or subsequential rest, the enzyme does not show any up- or down-regulation, which contrasts with the behavior of Na+, K+ ATPase.