Effect of Streptozotocin-induced Diabetes on Pancreatic Insulin Content of the Fetus

Abstract

Diabetes was produced in five-day pregnant Sprague- Dawley rats by intravenous injection of 40 mg./kg. body weight of streptozotocin. Normal pregnant rats were used as controls. Pancreases of the mothers and their offsprings were extracted by acid-alcohol and the insulin measured by immunoassay using rat insulin as a standard. Nonfasting blood sugar of the streptozotocin-treated pregnant rats was 285 ± 18 mg./100 ml. and their pancreatic insulin concentration was 5.9 ± 1 μg./gm. compared to 103 ± 3 mg./100 ml. and 44.2 μg./gm., respectively, in the normal rats. Fetal pancreases of streptozotocin-induced diabetic pregnant rats and normal animals were obtained on Days 18, 19, and 21 of gestation, and on Day 4 after birth. The pancreatic insulin concentration of fetuses of diabetic mothers rapidly and progressively increased from 8.0 ± 0.9 μg./gm. on Day 18 to a peak of 63.0 ± 9.0 /μg./gm. on Day 21. On Day 4 after birth, the value was 312 ± 109 μg./gm. The total pancreatic insulin content also progressively increased to a prenatal peak of 0.84 ± 0.15 μg. on Day 21. The pancreatic insulin concentration of fetuses of normal mothers was not significantly different from those of diabetic mothers. There was no correlation between the elevation of maternal blood sugar and the insulin concentration of the fetal pancreas. The total pancreatic insulin content of fetuses of diabetic rats was less than those offspring of the normal rats on Day 18 and Day 4 after birth, but was not significantly different on Days 19 and 21. The lower insulin content found in fourday-old rats born of diabetic animals was probably related to their inability to obtain adequate nourishment from their very sick mothers.