Changes in liver and gastric mucosal hexosamine synthesis after restraint.

The specific activity of L-glutamine: D-fructose-6-phosphate aminotransferase was measured in the oxyntic gland mucosa and liver of fasted, male rats after immobilization in a cold environment. Immobilization for 3 hr resulted in 100% frequency of lesion formation associated with decreased enzyme activity in oxyntic gland mucosa (70.1 plus or minus 5.9% of control) and liver 25.2 plus or minus 5.2% of control). Enzyme activity had returned to control level in the stomach 9 hr after immobilization, and in the liver 21 hr after immobilization. Immobilization for 1 1/2 hr decreased oxyntic gland mucosa enzyme activity to 21.0 plus or minus 9.8% of control, although the frequency of lesion formation was only 62.5%. Liver enzyme activity was 51.3 plus or minus 12.8% of control. Concentrations of UDP-N-acetylhexosamines, feedback inhibitors of this enzyme, were not altered in either tissue. Adrenalectomy, which increased the frequency of damage after 1 hr of immobilization, enhanced the decreases in enzyme activity in both tissues, while atropine sulfate, which decreased the frequency of damage after 3 hr of immobilization, had no significant effect on the enzyme. Thus, immobilization of rats in a cold environment decreases or alters the synthesis of hexosamine-containing compounds through a mechanism not dependent on acid secretion or adrenocorticoids. This alteration in synthesis may result not only in abnormal mucus secretion, but also in altered cell membrane structure and function.