A study was made of the insulin content of pancreases of nonpregnant, pregnant and postpartum rats and of their developing fetuses. The insulin content of the extracts was measured by radioimmunoassay, using crystalline rat insulin as a standard. The mean concentration of insulin in the pancreas of nonpregnant animals was 43 ± 6 μg./gm. The insulin concentration did not change significantly during late pregnancy or on day 4 postpartum. However, the weight of the pancreas was significantly greater in the pregnant and the postpartum rats. Thus, the total insulin content of the pancreas was greater in the pregnant and postpartum rats, being 23 ± 1.4 μg. and 24 ± 1.9 ng. respectively, as compared to 15 ± 0.7 μg. in the nonpregnant rats.
The fetal pancreases were obtained at five periods of gestation: daily from day 18 to day 22, and on day 4 after birth. The mean weight of the fetal pancreases progressively and significantly increased from 4.4 ± 0.3 mg. on day 18 to 14.1 ± 1.5 mg. on day 20. On day 4 after birth, the mean pancreatic weight was 15.1 ± 0.5 mg. The fetal pancreatic insulin concentration rapidly and progressively increased from 14 ± 2 μg./gm. on day 18, to 80 ± 9 μg./gm. on day 21, and by day 4 after birth was 621 ± 103 μg./gm. By day 21 the fetal pancreatic insulin concentration had reached the prenatal peak and was already twice that of the mother. The total fetal pancreatic insulin content showed a progressive increase during the fetal life from 0.07 ± 0.01 μg. on day 18, to 1.23 μg. on day 21, a seventeen fold increase.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.