Effects of streptozotocin‐induced diabetes on fetal development of the rat

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Abstract
The purpose of this study was to determine whether or not in rats with experimentally induced diabetes there is an increased frequency of congenital malformations; data in the literature are not consistent on this point. Virgin CD females rats were injected with 40–50 mg/kg streptozotocin (Stz) before mating (SIBM group) or on the first day of pregnancy (SI1). Both SIBM and SI1 females were divided into two groups according to their blood glucose levels: severaly diabetic (SD, > 300 mg%) and mildly diabetic (MD, 120–250 mg%). Food and water consumption by the control and MD groups were the same, but the SD females developed polyphagia, polyuria, and polydypsia, which continued to increase throughout pregnancy, as did the blood glucose levels. All the MD females mated and carried to term. In SD females both frequency of mating and fertility were only slightly lower than in the controls. All the females were killed on the 21st day of pregnancy. Pre- and postimplantation losses were the same for diabetic and control rats, but SIBM-SD females ovulated less than other groups. Weights of fetuses of SD dams were lower and blood sugar levels higher than those of the other groups. The placentas of SD rats were significantly heavier and there was cystic degeneration of spongiosa. The incidence of major malformations was minimal ( ∼ 2%) in fetuses of SD females and there were none at all in controls or MD females. In conclusion, our data are in agreement with those of other investigators who have found that rats with experimentally induced diabetes have smaller fetuses and increased placental weight. But our data do not show any increase in incidences of malformations or of fetal loss, which have been reported by some groups. One basis for this disagreement might be the differences in the composition of the diets, especially in mineral salt content. We are currently investigating this possibility.