Arginine in poultry nutrition

Arginase assayBirds were killed by dislocation of the neck and were bled.The kidneys and liver were removed immediately.Since it was generally inconvenient to assay the activity of a large number of samples immediately, they were all stored for a standard period of 3-4 days at -15' to ensure uniformity, care being taken to avoid desiccation.Samples of tissue were homogenized in an all-glass Potter & Elvehjem (1936) homogenizer cooled in ice.T h e homogenizing medium was a buffered solution containing manganous ions prepared according to the recipe of Greenberg ('95 I) : 5.8 g maleic acid were dissolved in 400 ml water and the pH was adjusted to 9.7-9-8 with N-NaOH.This solution was added to 25 ml z M-MnSO, and the whole made up to I 1.T h e final p H was approximately 7 and the solution equivalent to 0.05 M.More dilute buffers were prepared from this by dilution (which slightly raises the pH) and addition of sufficient of a maleic acid-manganous sulphate solution of the required molarity to readjust the pH to 7.0.For use as a homogenizing medium the solution was diluted in this way to 0'001 M and adjusted to pH 7.0.A 6 ml volume of the homogenizing medium was added to a I g (wet weight) sample of tissue in the homogenizer and the pestle rotated at 2000 revlmin for from 0.5 to I min.T h e contents of the tube were transferred to a measuring cylinder and made u p to 10 ml.T h e following standard homogenate concentrations were used for the assay: for rat kidney and chick liver and kidney preparations 20 and 10 mg/ml; for rat liver I and 0.5 mg/ml.T h e homogenates were pre-incubated at 37" for a period of 60-80 min before assay, i.e. before any addition of substrate.This procedure ensured a standard equilibration with cofactor.