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Biomedical subjects

E White

Publications and source records attributed to E White.

At least 361 records · Page 20Linked to original sources
PubMed1979

Age-dependent changes in the response of the lamb ductus arteriosus to oxygen and ibuprofen.

Circular strips of ductus arteriosus from lambs of gestational age between 90 and 144 days (term 147 days) were studied in vitro at low (8--16 torr (1 torr = 133.322 Pa)) and high (426--622 torr) PO2. Potassium- and oxygen-induced contractions increased with the gestational age and attained a maximum at term. At low PO2, ibuprofen, a blocker of prostaglandin synthesis, produced a dose-dependent contraction of the ductus at all ages and enhanced the potassium-induced contraction of the immature ductus (90--124 days). Both effects were relatively greater in the 103- to 107-day gestational group. At that age, ibuprofen also potentiated the oxygen-induced contraction. These findings, while confirming that a prostaglandin is involved in ductus patency, indicate that the prostaglandin-relaxing mechanism becomes functional at an early stage of gestation and reaches maximal activity before term. The existence of an active, prostaglandin-mediated relaxation in the preterm ductus may account, in part, for the reduced responsiveness of the vessel to oxygen. It is confirmed that ibuprofen and other nonsteroidal antiinflammatory drugs are well suited for the management of the premature infant with patent ductus arteriosus.

Animals↗
PubMed1978

Prostaglandin I2 is less relaxant than prostaglandin E2 on the lamb ductus arteriosus.

Prostaglandin (PG) I2 and its stable metabolite, 6-keto-PGF1alpha, were tested on the isolated ductus arteriosus from mature fetal lambs. PGI2 relaxed the ductus in high doses (threshold 10(-6)M) and its activity disappeared on standing at room temperature for 30 minutes. 6-keto-PGF1alpha was inactive at all doses. By contrast, PGE2 produced a dose-dependent relaxation over a range between 10(-10) and 10(-6)M. These findings confirm that PGE2 is the most potent ductal relaxant among the known derivatives of arachidonic acid. PGE2 probably maintains ductus patency in the fetus and, together with PGE1, remains the compound of choice in the management of newborns requiring a viable ductus for survival.

Animals↗
PubMed1978

Action of prostaglandins, endoperoxides, and thromboxanes on the lamb ductus arteriosus.

Prostaglandin (PG) E2, the PG endoperoxides PGG2 and PGH2, and enzymatically generated PGI2 and thromboxane A2 (TXA2) were tested in vitro on circular strips of ductus arteriosus from mature fetal lambs. Both PGE2 and the PG endoperoxides produced a dose-dependent relaxation of the ductus at low PO2 (7-11 torr), and their action was reduced or abolished at high PO2 (410-660 torr). PGE2, however, was more potent than the endoperoxides. The reaction mixture containing PGI2 relaxed the hypoxic ductus, but this response was not due to PGI2 but to two, more stable and as yet unidentified, compounds, one of which is most certainly PGE2. TXA2 was inactive on the vessel at low and high PO2. These results confirm that PGE2 is the most effective PG acting on the ductus and provide further support to the hypothesis that this PG is responsible for patency of the vessel during fetal life. PGE2 action, however, may be complemented by that of another endoperoxide derivative formed in the PGI2 synthetic reaction which remains to be identified.

Animals↗
PubMed1977

Prostaglandins and the control of muscle tone in the ductus arteriosus.

Several lines of evidence implicate E-type PGs in the maintenance of patency of the foetal ductus arteriosus. The PGE mechanism is functional in man, sheep, rat and rabbit, but it is seemingly absent in guinea pig. The role of the PGs in the closure of the vessel at birth is uncertain. Work with different species suggests that as PO2 rises at birth the relaxant effect of PGEs on the ductal muscle decreases. This decreased sensitivity may facilitate the oxygen triggered contraction. The calf ductus is an exception and its closure may be mediated by PGF2alpha. An important fact emerging from this review is that species may differ with regard to the occurrence and possible function of the PGs in the ductus arteriosus. The significance of these differences to the function of the oxygen-sensing mechanism remains a major question for future research.

5,8,11,14-Eicosatetraynoic Acid↗