Effect of deficient and excess dietary vitamin B-6 on amino transaminase and glycogen phosphorylase activity and pyridoxal phosphate content in two muscles from postpubertal gilts.

Postpubertal gilts averaging 111 kg and gaining 2.7 kg/wk were fed daily 1.9 kg/d of a diet providing 0.45, 2.1 or 83 mg of vitamin B-6/d. An additional group of animals were fed the high vitamin B-6 diet providing 83 mg of vitamin B-6/d for the initial 57 d of the experiment and then switched to 0.45 mg of vitamin B-6/d for the remainder of the 121-d experiment (61 gilts total). On d 0, 57 and 121, animals from each treatment were killed, and samples of the semitendinosus (ST) and semimembranosus (SM) were removed. Glutamic-oxaloacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT), glycogen phosphorylase and pyridoxal phosphate (PLP) were measured in muscle tissues. The erythrocyte GOT activity coefficient indicated that gilts consuming 0.45 or 2.1 mg of vitamin B-6/d developed a vitamin B-6 deficiency. A vitamin B-6 deficiency resulted in the loss of whole-muscle transaminase activity (enzyme activity X muscle weight) with little effect on whole-muscle total phosphorylase or total PLP content. Excess dietary vitamin B-6 increased whole-muscle total PLP and total phosphorylase content with small decreases in whole-muscle transaminase. Under these conditions, muscle tissue acts as a nonmobile reservoir of PLP. Sixty to 95% of muscle PLP was bound to muscle glycogen phosphorylase.