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 m aternofetal flux of calcium (Ca) and magnesium (Mg), calbindin(9K) mRN A expression, and net fetal Ca and Mg accretion has been investigated using control (C), untreated diabetic (D-0) and insulin-treated diabet ic (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 m aternofetal flux of magnesium in the Do group was 79 and 66% of the va lue in the C and D-1 groups. Fetal Ca and Mg content (mmol; mean +/- S EM) was also significantly lower in the D-0 group compared with the ot her 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 significan tly lower in D-0 group when normalized to fetal ash weight. Densitomet ric 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 an d D-1 groups. Collectively, the data suggest that untreated maternal d iabetes mellitus reduces fetal Ca and Mg accretion by an effect on the expression of placental transport components involved in the maternof etal transfer of these cations.