Abstract
Hypoxia is associated with high concentrations of total plasma β-EP in both human umbilical cord and fetal lamb. To characterize this endorphin activity we used RIA to measure AC β-EP (antibody reacts <1% with β-EP) and total plasma β-EP (antibody reacts equally with β-EP and AC β-EP). 9 fetal lambs were studied before and after exposure of the pregnant ewe to 10% O2 × 30 min with and without fetal dexamethazone pretreatment. In 13 hypoxia studies (PaO2 22±1 to 12±1 mmHg), AC β-EP remained unchanged (85±11 and 109±14 pg/ml mean ±S.E.) while total β-EP increased (102±21 to 557±165 pg/ml, p<.01). Thus it is likely that inactive AC β-EP is the major endorphin species in the unstressed fetus while biologically active β-EP increases with hypoxia. In 5 hypoxia studies dexamethazone pretreatment had no effect on AC β-EP level while the increase in total β-EP was blunted (108±25 to 158±12 pg/ml). There was an inverse correlation of AC β-EP with gestational age (R=-0.49, p<.01, 113-142d, N=28). The total β-EP response to hypoxia was less before than after 130 d gestation. Thus biologically inactive AC β-EP released by the unstressed fetus in decreasing amounts toward term is unaffected by hypoxia or glucocorticoids while active β-EP release is increased by hypoxia and suppressed by glucocorticoids. Speculation: Data are consistent with diminution in tonic activity of intermediate (AC β-EP release) and enhancement of anterior β-EP release) pituitary activity with gestational maturation.
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Stark, R., Wardlaw, S., Daniel, S. et al. CHARACTERIZATION OF β-ENDORPHIN ACTIVITY IN THE FETUS: ACETYLATED β-ENDORPHIN (AC β-EP) AND TOTAL β-ENDORPHIN (β-EP) DURING HYPOXIA. Pediatr Res 18 (Suppl 4), 177 (1984). https://doi.org/10.1203/00006450-198404001-00507
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DOI: https://doi.org/10.1203/00006450-198404001-00507