Prostanoid production in umbilical vessels and its relation to glucose tolerance and umbilical artery flow resistance

To study prostanoid synthesis in umbilical vessels relative to maternal glucose tolerance and umbilical artery blood flow resistance.

Umbilical artery pulsatility index was determined by Doppler velocimetry in 21 women with diabetes or impaired glucose tolerance and 10 healthy women. Segments from the umbilical artery and vein were incubated and prostacyclin (PGI2) and thromboxane (TxA2) metabolites determined. Statistical analyses with the Mann-Whitney U test, Kruskal-Wallis test, Wilcoxon signed-ranks matched-pairs test, contingency table analysis, Fisher's exact test, and simple linear regression analysis were used and a two-tailed P value of < 0.05 considered statistically significant.

No significant difference in PGI2 or TxA2 production was found in umbilical vessels between the women with diabetes/impaired glucose tolerance and controls, but the PGI2/TxA2 ratio in the vein was significantly lower in the diabetes/impaired glucose tolerance group. The umbilical artery pulsatility index was positively correlated to the PGI2/TxA2 ratio in cord vessel segments and to cord plasma TxA2 concentration. The cord plasma TxA2 concentration was significantly higher in cases with a high umbilical artery pulsatility index. The prostanoid production was not correlated to maternal HbA1c or cord plasma C-peptide concentrations.

In association with diabetes, an increased 'peroxide vascular tone' and an enhanced 'endoperoxide shift' between platelets and vascular endothelium may explain the unexpected positive correlation found between the umbilical artery pulsatility index and the vascular PGI2/TxA2 synthesis ratio.