Skeletal muscle cellularity and histochemistry in young lean and obese pigs

The cellularity and histochemistry of the semitendinosus muscle was studied in lean and obese pigs at 14 days of age. Muscles from lean animals had lower (P less than .05) muscle weights and minimum fiber diameters and had reduced (P less than .05) percentages of dry matter and protein when contrasted to obese muscles. Concentrations of RNA and glycogen were independent of animal strain but DNA levels were severely depressed (P less than .01) in obese muscle. Histochemistry for lipid, NADH-TR, acid ATPase, esterase and glycogen (PAS) indicated no strain effects. Regardless of strain, sections from larger animals showed histochemical patterns indicative of more mature muscles. These studies demonstrate abnormalities in muscle cellular characteristics in the young obese animal. Furthermore, these abnormalities may accelerate muscle maturation and hasten the fattening phase of growth.