Some quantitative biochemical evaluations of developing skeletal muscles in the human foetus.

This study was performed to obtain a more precise quantitative estimation of oxidative and glycolytic potentials and stores of various substrates of the muscles in the human foetus. The material consisted of muscle samples from different muscles, a total of 166 muscle specimens from 65 foetuses and 55 skeletal muscle specimens from 53 infants and children. The latter samples were obtained at surgery. The activities for succinate dehydrogenase and phosphofructokinase were chosen as markers for mitochondrial and cytoplasmatic enzymes respectively. Glycogen, triglyceride and phosphagen levels were studied. Water and protein content of the muscle tissue undergo continuous changes during foetal life and were therefore also included in the study. The SDH activity was low during gestation and reached a value of 2-3 mmoles/kg w.wt. X min at delivery. The PFK activity was also low during gestation, but around 25 weeks gestation a value of 3-4 mmoles/kg w.wt. X min was common, and around delivery time about 7 mmoles/kg w.wt. X min. At 1-5 years the PFK activity was around 11-12 mmoles/kg w.wt. X min, which is similar to adult muscles. Glycogen content varied, but increased during gestation. In the last trimester of gestation a value of 62-92 mmoles units/kg w.wt. was found. The triglyceride content at the end of the gestation time was 3-16 mmoles glycerol/kg w.wt. The phosphagen levels were quite low all through foetal life, averaging between 0.5 and 3 mmoles/kg for ATP and CP concentrations.