Effects of muscle stimulation in situ in pregnant rats.

Effects of muscle stimulation were studied in the perfused hindleg of late pregnant and age-matched control rats. Muscle stimulation increased tissue glucose uptake in both groups with a tendency towards higher values in the pregnant rats. The stimulation-induced lactate production was markedly larger in pregnant than in control rats. In the pregnant rats muscle tension output decreased more rapidly and vascular resistance was greater than in non-pregnant group. The decline of tension, accompanied by the enhanced lactate production of contracting muscles, may suggest a reduced muscle oxidative potential in late pregnancy and/or delayed adaptation of the local blood flow. The greater vascular resistance found during muscle stimulation in pregnant animals might have been due to the persistent local action of estrogens. The data obtained indicate that pregnancy modifies skeletal muscle function during stimulation in situ.