Abstract
The effects of nutritional and hormonal treatments on the activities of rat liver phenylalanine hydroxylase (Phe H) were studied. When a non-protein diet was substituted for the high protein diet, Phe H activities fell rapidly and remained constant from Day 7, whereas when rats were starved for 10 days, Phe H activities were slightly decreased. In case of protein-depleted rats fed a 15% casein diet for 8 days, Phe H activities were again increased. However, excess feeding of tryptophan or phenylalanine delayed the return of Phe H activity to the control level. Neither glutamic acid, lysine nor threonine had effect when fed in excess. In rats fed an amino acid diet devoid of only phenylalanine, recovery of Phe H activity was inferior to that of rats fed a complete diet, but only slight recovery of Phe H activity was observed in rats fed a phenylalanine-tyrosine deficient diet. Doses of cortisone did not respond to Phe H in the liver of intact and adrenalectomized rats. Alloxan diabetic treatment to rats also did not have effect on this enzyme activity.
