Glucoregulation during progressive starvation in late pregnancy in the rat

The response of glucose utilization (transport and phosphorylation) by individual skeletal muscles to progressive starvation in late pregnancy in the rat was investigated in relation to changes in whole body glucose turnover. Compared with insulin-stimulated values, the decline in muscle glucose utilization evoked by short-term (6-h) starvation was about twofold greater in pregnancy. Suppression of glucose utilization by slow-twitch muscles was observed as the starvation period was extended from 6 to 24 h only in unmated rats. Extending starvation to 24 h did not further reduce glucose utilization by fast-twitch skeletal muscles in either group. Suppression of whole body glucose disposal was observed between 6 and 24 h of starvation in unmated, but not pregnant, rats. The results demonstrate that metabolic adaptation of almost complete suppression of glucose utilization by slow-twitch muscle, normally elicited only by prolonged (24-h) starvation, is already established after acute (6-h) starvation in late pregnancy. The present study supports the concept of "accelerated starvation" in late pregnancy with respect to muscle glucose utilization after short-term food withdrawal but demonstrates that further glucose conservation cannot be achieved after more prolonged starvation.