OSMOTIC DIARRHEA AND SKELETAL-MUSCLE PROTEIN-SYNTHESIS IN-VIVO

The pathogenic nature of the wasting seen in diarrhoea is unknown. Thi s study measured protein synthesis in an established model of diarrhoe a using lactose for seven days. Comparisons were also made with data o btained from rats fed an identical diet in which lactose was replaced by isocaloric glucose ad libitum (that is, the control diet). To accou nt for diarrhoea induced anorexia, a third group of rats were included , which were fed identical amounts of the control diet as the rats wit h diarrhoea inducing diet. Comparisons of the diarrhoea induced group with rats fed the control diet ad libitum showed that diarrhoea caused a significant reduction in body weights. Type I and type II muscles s howed significant reductions in protein, RNA, and DNA contents, as wel l as a fall in the derived parameters, RNA/DNA, protein/DNA, and RNA/p rotein. Fractional rates of protein synthesis (k(s)) were also reduced . However, synthesis rates of type I and II muscles relative to RNA (k (RNA)) were unchanged in these muscles in diarrhoea induced rats compa red with ad libitum fed controls. In the jejunum there was an increase in the RNA/DNA ratio, and reductions in k(s) and k(RNA). Comparisons were also made between rats with diarrhoea and rats pair fed the contr ol diet. There were no changes in total muscle protein, RNA or DNA con tents. This suggests that an important feature of body wasting in diar rhoea is the element of anorexia, which induces severe metabolic chang es. The comparison between rats with diarrhoea and the pair fed group showed that histological features of the plantaris were not overtly ch anged, though diarrhoea caused significant reductions in RNA/DNA, prot ein/DNA, k(s), and k(RNA). Similar changes were seen for the soleus; t hough the reduction in k(s) failed to attain statistical significance. In the jejunum a comparison of diarrhoea induced rats with pair fed c ontrols, showed increases in the ratios of RNA/DNA and protein/DNA.