. Decreased contraction-stimulated glucose transport in isolated epitrochlearis muscles of pregnant rats. J Appl Physiol 98: [1021][1022][1023][1024][1025][1026][1027] 2005. First published November 5, 2004; doi:10.1152/japplphysiol.00953. 2004.-Late pregnancy is characterized by insulin resistance for glucose transport in skeletal muscle. The main purpose of this study was to investigate the effect of late pregnancy on contraction-stimulated glucose transport in isolated rat skeletal muscle after in vitro electrical stimulation. Isolated epitrochlearis muscles of 19-day pregnant and aged-matched nonpregnant control rats were studied. One muscle from each rat was stimulated to contract, and the contralateral muscle served as a resting control. Tension developed during contractile activity, 3-O-methylglucose (3-MG) transport rate, and glycogen concentration were determined. Epitrochlearis muscles from other rats were used to measure insulin-stimulated 3-MG transport. There was no detectable difference between the nonpregnant and pregnant groups for contractile performance (peak tension, total tension, or fatigue). Pregnancy was not associated with significant changes in muscle glycogen concentration (resting or after contractile activity) or the contraction-stimulated decrement in glycogen concentration. For muscles from pregnant vs. nonpregnant groups, there was a 22% reduction (P Յ 0.05) in contraction-stimulated glucose transport, a 28% decrease (P Յ 0.05) in insulin-stimulated glucose transport, and unchanged basal glucose transport. In conclusion, isolated epitrochlearis muscles from pregnant vs. nonpregnant rats had a relative decrement in contraction-stimulated glucose transport that was similar to the relative decline in insulin-stimulated glucose transport. The decrement in contraction-stimulated glucose transport was not attributable to pregnancy-related changes in tension development or glycogen levels. The similar relative decline in insulin-and contraction-stimulated glucose transport raises the possibility that pregnancy impairs a distal process that is common to mechanisms whereby each stimulus activates glucose transport. insulin resistance; gestational diabetes; fatigue; glycogen LATE PREGNANCY (gestational days 18 -22 in the rat, third trimester in humans) is characterized by whole body insulin resistance (8, 27). Insulin-stimulated glucose disposal by skeletal muscle during a euglycemic-hyperinsulinemic clamp is reduced in pregnant compared with nonpregnant rats (27). Insulin resistance is also a normal characteristic of late pregnancy in humans, presumably to ensure adequate availability of maternal nutrients to the fetus during this period of rapid growth (5, 25). Toyoda et al. (36) reported decreased insulinstimulated glucose transport in isolated epitrochlearis muscles of late pregnant rats compared with nonpregnant controls, demonstrating a decrement in the intrinsic capacity for insulinstimulated glucose transport in skeletal muscle, independent of systemic factors that influence whole ...