Relationship Between the Effects of Contraction and Insulin on the Metabolism of the Isolated Levator Ani Muscle of the Rat

The effects of repetitive contractions of the isolated levator ani muscle of the immature male rat were investigated on glucose uptake, the accumulation of D-xylose- 14 C, and α-aminoisobutyric acid- 14 C (AIB-14C) as well as on the incorporation of leucine- 3 H, proline- 3 H and valine- 14 C into protein and adenine- 14 C into RNA. These effects were compared with the effects of insulin. Glucose uptake and D-xylose- 14 C accumulation were increased during the period of contractions and after this period for at least three hours. Insulin and contractions had additive effects on these uptakes. AIB- 14 C accumulation was also stimulated by contraction. This effect increased with the incubation time and was maximal at a frequency of 60 imp/min. The effect lasted for at least three hours after the period of contractions. The stimulating effect of insulin on AIB- 14 C accumulation in the muscle was reduced by contractions. A reduction was also obtained on the incorporation of normal amino acids into protein as well as on the incorporation of adenine- 14 C into RNA. The stimulating effect of insulin on the rate of incorporation of amino acids into protein was reduced during the contraction period. No insulin-like activity could be found in the media of contracting muscles, when these media were tested with fresh muscles for effects on the accumulation of AIB- 14 C or D-xylose- 14 C.