EFFECT OF DIABETES-MELLITUS ON MATERNOFETAL FLUX OF CALCIUM AND MAGNESIUM AND CALBINDIN(9K) MESSENGER-RNA EXPRESSION IN RAT PLACENTA

The effect of maternal diabetes mellitus on placental unidirectional maternofetal flux of calcium (Ca) and magnesium (Mg), calbindin(9K) mRNA expression, and net fetal Ca and Mg accretion has been investigated using control (C), untreated diabetic (D-0) and insulin-treated diabetic (D-1) rats. Unidirectional maternofetal flux of Ca in the D-0 group was 61 and 63% of the value of the C and D-1 groups; unidirectional maternofetal flux of magnesium in the Do group was 79 and 66% of the value in the C and D-1 groups. Fetal Ca and Mg content (mmol; mean +/- SEM) was also significantly lower in the D-0 group compared with the other two groups (0.111 +/- 0.004 versus 0.153 +/- 0.008 in C and 0.168 +/- 0.007 in D-1, p < 0.01 D-0 versus C and D-1 for Ca; and 0.021 +/- 0.001 versus 0.027 +/- 0.001 in C and 0.031 +/- 0.001 in D-1, p < 0.01 D-0 versus C and D-1 for Mg). However, only Ca content was significantly lower in D-0 group when normalized to fetal ash weight. Densitometric analysis of autoradiograms after Northern hybridization with cDNA probes demonstrated that the placental calbindin(9K)/cyclophilin mRNA ratio was 11- to 12-fold lower in the D-0 group compared with the C and D-1 groups. Collectively, the data suggest that untreated maternal diabetes mellitus reduces fetal Ca and Mg accretion by an effect on the expression of placental transport components involved in the maternofetal transfer of these cations.