The main determinant of muscle carnosine (M-Carn) content is undoubtedly species, with, for example, aerobically trained female vegetarian athletes [with circa 13 mmol/kg dry muscle (dm)] having just 1/10th of that found in trained thoroughbred horses. Muscle fibre type is another key determinant, as type II fibres have a higher M-Carn or muscle histidine containing dipeptide (M-HCD) content than type I fibres. In vegetarians, M-Carn is limited by hepatic synthesis of β-alanine, whereas in omnivores this is augmented by the hydrolysis of dietary supplied HCD’s resulting in muscle levels two or more times higher. β-alanine supplementation will increase M-Carn. The same increase in M-Carn occurs with administration of an equal molar quantity of carnosine as an alternative source of β-alanine. Following the cessation of supplementation, M-Carn returns to pre-supplementation levels, with an estimated t1/2 of 5–9 weeks. Higher than normal M-Carn contents have been noted in some chronically weight-trained subjects, but it is unclear if this is due to the training per se, or secondary to changes in muscle fibre composition, an increase in β-alanine intake or even anabolic steroid use. There is no measureable loss of M-Carn with acute exercise, although exercise-induced muscle damage may result in raised plasma concentrations in equines. Animal studies indicate effects of gender and age, but human studies lack sufficient control of the effects of diet and changes in muscle fibre composition.

Muscle Carnosine (M‐Carn) synthesis is limited by the availability of ?‐Alanine ( ?‐Ala) but can be increased by supplementation with ?‐Ala. This is of interest to athletes since increased levels of muscle M‐Carn have previously been shown to improve exercise performance. Above 10mg/kg bwt, however, ?‐Ala in solution or rapidly‐dissolving capsules causes symptoms of paraesthesia, despite the amount being less than that available from normal meat ingestion.PURPOSETo investigate the change in M‐Carn in subjects supplemented with a controlled‐release ?‐Ala formulation.METHODSeven males received 2x800mg ?‐Ala controlled release tablets, 4/d for 4w. Controlled release tablets were Carnosyn(tm) supplied by Collegiate Sports Nutrition. A muscle biopsy from the vastus lateralis was taken at 0 and 4w, and 3 and 6w post supplementation. No control group was included as several previous studies have demonstrated no change in M‐Carn without ?‐Ala supplementation.RESULTSSubjects did not experience paraesthesia. Mean (±SD) M‐Carn at 0 and 4w, and, 3 and 6w post supplementation were 25.9±4.3, 41.3±5.5, 38.3±6.7 and 35.4±5.5 mmol.kg−1 dry muscle. Post supplementation M‐Carn declined via first‐order kinetics with a half‐life (t½) determined to be 8.6w.CONCLUSIONThe controlled release ?‐Ala formulation was effective in raising M‐Carn. Following supplementation, levels of M‐Carn declined slowly with a t½ ~9w.

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Several brands of microaggregate blood filters were evaluated in vitro and in vivo for their effect on plasma free hemoglobin and platelet count, both while new and after prior usage.Time required for passage of diluted packed red cells was also determined. The authors conclude that, although the use of microaggregate filters for multiple transfusions is commonly accepted, their use with fresh blood may decrease platelet count. Filtration characteristics and administration time should be considered in selection of filters.

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