Comparative and evolutionary adaptation of muscle buffering capacity in species subject to varying degrees of acidosis.

The Histidine (His) dipeptides, Carnosine (β‐AlaHis) Anserine (β‐Ala‐1‐methylHis) and Balenine (β‐Ala‐3‐methylHis) are ubiquitous in muscle of vertebrates and invertebrates. Their major function appears to be H+ buffering in muscle, with the imidizole ring of the His residue having a pka of 6.7–7.1. Species variations in the quantity of His‐dipeptides appears to be proportional to the level of anerobically generated H+ ions during naturally encountered bouts of exercise. Whale muscle, which contains the highest level of His‐dipeptide of any species (>350 mmol.kg −1 dm), is subjected to the greatest levels of anaerobic acidosis during prolonged oxygen deprivation. Pectoral muscle from birds such as wild pheasant (~220) have evolved high levels to combat H+ ions generated by explosive flight, a requirement for survival, but also a vestigial feature in the chicken (~225) and turkey (~275). Horses (~110), dogs (~82) and racing camels (~70) have selectively adapted higher muscle levels to counteract acute acidosis during sprints required for escape, hunting or racing. Humans, in contrast, have much lower levels; V lateralis in body builders (~44), omnivores (~23) and vegetarians (~13) are consistent with less need for sprinting for survival. CONCLUSION: Comparative levels of His‐dipeptide in muscle from different species are reflective of the relative need for H+ buffering indicating evolutionary adaptation.