However, the authors did not examine an alternative hypothesis that the infusion of balanced amino acids (similar to trout body proteins) might have led to amino acid excretion without deamination and an enhanced oxygen uptake. Brown and Cameron (1991) provided data that suggest that the infusion of free amino acids to catfish caudal aorta may be associated with increased oxygen consumption due to protein synthesis. In both studies, the site of ‘dietary’ amino acid infusion was highly unusual, and not physiologically rational, and neither protein synthesis nor direct amino acid excretion was accounted for. In other words, the conclusions are highly speculative. The most recent results of Saavedra, Conceição, Helland, Pousão-Ferreira and Dinis (2008) can be interpreted as providing evidence that ‘acute’ supplementation of FAA recognized as deficient, based on its content in the compound (formulated) diet, does not ensure a significant impact on protein synthesis. The synthesis rate is due to ‘recirculation’ of the significant pool of amino acids through protein degradation, both in the metabolic, regular proteolysis-renewal processes, and most importantly, through proteosomally degraded ‘defective’ proteins that are almost instantly hydrolysed after ‘faulty’ synthesis (Vabulas & Hartl 2005).