Insulin-resistance during pregnancy and progesterone treatment in the rat

Changes in activity and intra-acinar distribution of glucose-6-phosphate dehydrogenase and malic enzyme during pregnancy in rat liver

Using techniques of microdissection and microassay as well as qualitative histochemistry the activity and intra-acinar distribution of G6PDH and ME were studied on selected days of pregnancy in the rat. Both enzymes show distinct fluctuations during the course of pregnancy in keeping with changes in hepatic lipogenesis. Marked increases in activity are seen as early as the 4th day, while highest values are attained on day 20, with a predominant perivenous induction. On day 22, just before parturition a sharp decrease of both enzyme activities with a flattening of the periportal/perivenous gradient was detected. G6PDH shows proportionally considerably larger increases and more distinct changes in zonation. The perivenous fluctuations in G6PDH activity of late gestation are supposed to be caused primarily by insulin. Although estrogen is known to induce both enzymes, the temporal changes in enzyme activity in pregnancy cannot be related to the action of estrogen alone. The changes in enzyme activity, however, correspond well to those of progesterone, and although no direct action of progesterone on these enzymes has yet been proposed, further work on its effects on enzyme activity and distribution is indicated.

Pregnancy and diabetes: the maternal response

Pregnancy places remarkable stresses on maternal carbohydrate metabolism and pancreatic insulin reserves. The normal mammal responds to pregnancy by increasing pancreatic islet size and insulin secretion. Pregnancy also causes alterations in concentrations of metabolic fuels in maternal circulation. These changes are partly attributed to gestational increases of estrogen, progesterone and human chorionic somatomammotropin, and are thought to provide a proper metabolic and hormonal incubation medium for the fetus. Conversely, the compromised pancreas of the diabetic is unable to meet the additional demands of pregnancy, and carbohydrate metabolism deteriorates. The character of these metabolic changes depends on the time of gestation and the type of diabetes mellitus.