At the end of each treatment phase , fasted subjects received a @ mol/L per kg bolus injection of -LSB- @,@,@ - ( @ ) H@ -RSB- - l-Leucine immediately followed by constant infusion of -LSB- @,@,@ - ( @ ) H@ -RSB- - l-Leucine ( @ mol L ( -@ ) kg ( -@ ) h ( -@ ) ) for @ hours , and blood samples were collected .