Effect of the RN(-) gene on ultrastructure and protein fractions in pig muscle.

The aim of the present experiment was to study the effect of the RN(-) gene on ultrastructure of white fibres and the proportion of the different protein fractions in Longissimus lumborum muscle of RN(-) pigs. The ultrastructure of muscle was observed in 4 RN(-) carrier pigs and 4 rn(+)rn(+) homozygous pigs by mean of electron microscopy. Protein fractionation and quantification were performed on muscle from a second group of 4 RN(-) and 4 rn(+) pigs. No change in the proportions of the different protein compartments was observed. The abnormality of the glycolytic fibres of RN(-) pigs seems to be rather due to an increase of the glucid concentration in the sarcoplasm, perhaps secondarily to a modified osmolarity in the intracellular medium.