Week-old lambs received an
intravenous injection of 4.3, 8.5, 12.8 or 17.1 mmol [3H]
valine/5 kg
body weight, i.e., 3.6-14.4-times the whole-body free
valine content. To ensure that
protein synthesis measurements in lambs are reliable within a 30-min period, these large amounts of
valine must account for at least around 11-times the total free pool of
valine. This amounted to 12.8 mmol
valine/5 kg
body weight. There were no significant variations in plasma
insulin and plasma
glucagon levels 5, 13 and 30 min after the injection of so much
valine. The fractional rates of
protein synthesis were determined in tissues of animals receiving either 12.8 or 17.1 mmol
valine/5 kg
body weight. The rates of
protein synthesis in the jejunum (87.5%/day), liver (106.6%/day) and tensor fasciae latae muscle (18.8%/day) of lambs injected with the 12.8 mmol [3H]
valine flooding dose, were in the range of data obtained in immature rats. Increasing the flooding amount of
valine up to 17.1 mmol/5 kg
body weight did not significantly alter
protein synthesis rates in the jejunum, liver or skeletal muscle. This suggested that both the flooding-dose method in itself and
valine had no effect on in vivo
protein synthesis.