The timing of fetal B cell hyperplasia in diabetic rat pregnancy.

Fetal pancreatic development was measured in terms of total organ DNA and insulin concentration (ng/migrogram DNA) in the offspring of rats made mildly diabetic by intraperitoneal streptozotocin injection (60 mg/kg) on the first and second day of life. On day 20 the mean pancreatic insulin concentration of fetuses of diabetic mothers was significantly higher than that of controls (27.8 versus 20.8 ng/microgram DNA) but no significant difference was observed on day 18 (4.47 versus 4.68 ng/microgram DNA), day 16 (0.64 versus 0.77 ng/microgram DNA) or day 14 (0.04 versus 0.03 ng/microgram DNA). No significant difference in total pancreatic DNA was observed between test and control animals on day 14, 16, 18 or 20 of gestation. It is concluded that maternal streptozotocin diabetes alters the development of the differentiated fetal B cell (20 days) but has no effect on the protodifferentiated B cell (14 days), or during the period of secondary transition (16-18 days).