Liver glutamine synthetase activity and time courses of blood and urinary nitrogenous compounds after injection of methionine sulfoximine at various dosages in chickens fed a low protein diet.

Abstract

Methionine sulfoximine (MSM) was injected into chickens fed 5% protein diet at dosages of 20, 50, 75 and 100mg/kg body wt. The remaining activity of liver glutamine synthetase 7hr after dosing decreased with an increase of its dose, ranging from 12% to 6% of the control activity. The decreased plasma glutamine concentration 1.5hr after MSM treatment or later became low as a dose of MSM was increased. Blood ammonia concentration sharply increased up to 2.5hr after a transient unchange or fall and reached the steady state level at 4.5hr which was in proportion to MSM-dose. At 4.5hr the blood ammonia concentration was inversely correlated with plasma glutamine concentration (r=0.679). The rate of urinary excretion of ammonia rapidly increased for the first 3-4hr in similar manners and magnitudes in all chickens treated with MSM except 20mg MSM-dose. Almost the same time course patterns of plasma uric acid or urinary uric acid excretion in the doses of 50, 75 and 100mg tended to be low between 1 and 4hr after dosing as compared with 20mg MSM-dosed and control chickens. Any doses of MSM gave no effect on excretion of total urinary nitrogen. It is concluded that each of the time courses of blood glutamine, ammonia and uric acid and of urinary ammonia, uric acid and total nitrogen responds to a dose of MSM in similar manners at low and high protein intakes.