The effect of oxytocin, prostaglandin E2 and acetylsalicyclic acid on flowdistribution and on the transfer of alanine, glucose and water in isolatedperfused guinea pig placentae

The influence of oxytocin (OXY), sulproston (SUL) and acetylsalicylic acid (ASA) on L-alanine- (ALA), D-glucose- (GLU) or water- (H2O) uptake (materna l side) in the isolated perfused guinea pig placenta was investigated. Upta ke was measured with a single injection, paired tracer dilution method. 'T5 0' values were derived from venous concentration curves (extracellular mark er) as the distance (sec) between two concentration values at 50 per cent o f peal; concentration. T50 values were regarded to reflect the change of fl ow distribution on the maternal side. On average, there was a significant apparent inhibition of GLU uptake (by 2 7.2 per cent from control values) by OXY as well as of ALA uptake by OXY (2 6.0 per cent), by ASA (56.6 per cent), and by SUL (56.7 per cent). The resp ective mean T50 values decreased significantly in the above groups by 15.9 per cent, 18.7 per cent (ns), 42.2 per cent and 56.7 per cent. However, it was not possible to generate dose-response curves whereas significant corre lations of uptake values with T50 values were found. There was no dose-resp onse relationship between T50 values and OXY or ASA concentrations but decr eased mean T50 values were found. For SUL a weak correlation of T50 and SUL concentration was found. The r-value of GLU uptake and T50 was 0.57, for H 2O uptake this value was 0.70, for ALA uptake the r-values were 0.51 (OXY), 0.35 (SUL) and 0.31 (ASA). Correlation of uptake and concentrations were n ot significant. We conclude that the 'inhibitory' effects of OXY, ASA and p robably SUL on placental transfer are unspecific and the consequence of how shifts from the placental exchange area to the uterine muscle. (C) 2000 Ha rcourt Publishers Ltd.