EFFECT OF INSULIN ON ENDOCRINE PANCREAS FUNCTION DURING LATE PREGNANCY IN THE RAT

To partly or completely satisfy the increasing demand for insulin, pre gnant rats were infused SC with human insulin (2.4 or 4.8 IU/day) from day 14 to day 20 of gestation. Cyclic control rats underwent the same procedure of 6 days of insulin-treatment. During the treatment all,st oups of rats were hypoglycaemic, but foetal survival was not affected. The low dose treatment prevented the characteristic rise of the insul in response to a glucose challenge during pregnancy, both in vivo and in vitro, while the high dose treatment suppressed the insulin respons e, as well as the pancreatic insulin content. The insulin responses an d insulin contents of pregnant rats were higher than those of the corr esponding cyclic control rats. These results support the hypothesis th at during gestation the increased insulin demand, due to the actions o f placental hormones, is the cause of the increased insulin secretion. However, it cannot be excluded that direct effects of placental hormo nes on the islets of Langerhans are also involved.