Transfer of Ritodrine and Norepinephrine in Human Placenta: in vitro Study

Makhseed²,

Alrayyes³

et al. 1998

Med Princ Pract

Objective: The transports kinetics of α-aminoisobutyric acid (AIB) has been investigated in the human placenta in vitro using perfusion of isolated placental lobules. Methods: NCTC 135 tissue culture medium diluted with Earle’s salt solution was used as the perfusate, and tritiated water was used as the reference marker. Results: The transport fraction of AIB averaged 13.2% of that of tritiated water in 5 single-bolus injection experiments. The differential transport rates for 10, 25, 50, 75 and 90% cumulative efflux in the fetal vein of the study and the reference substances differed significantly as well. The transport kinetic parameters as area under the curve, clearance, elimination constant, time for maximum response, absorption rate and elimination rate of the amino acid averaged 0.12, 19.8, 0.78, 1.28, 0.10 and 0.06 times, respectively. Plotting of relative AIB transport ratios as a function of perfusion time demonstrated the active nature of amino acid transport in our perfusion conditions. Conclusions: The transport and kinetic parameters employed in the study may be useful in assessing dynamic placental membrane function of A type amino acids and other substances in varying experimental conditions as well as in disease states.

Section: Discussionsupporting

confidence: 80%

“…Human placentae were collected post partum after uncomplicated pregnancies, and perfusion of suitable placental lobules was performed as previously described [7][8][9][10]. Briefly, fetal vessels of an isolated placental lobule were cannulated and perfused with NCTC 135 (Sigma Chem.…”

Section: Methodsmentioning

confidence: 99%

Transport Kinetics of Alpha-Aminoisobutyric Acid in the Perfused Human Placental Lobule in vitro

Makhseed²,

Alrayyes³

et al. 1998

Med Princ Pract

“…This finding, though apparently incon sistent with its low molecular weight (328.4 dalton) and hence expected high placental transfer, seems to fit with previous reports on placental clearance of comparable smallmolecular-weight substances [7][8][9], The high ionization of labetalol at physiological pH (pKa being 7.4 -8.7) seems to account for its low placental transfer, despite the molecule being relatively small [14].…”

Section: Discussionsupporting

confidence: 87%

Transfer of Labetalol in the Perfused Human Placenta: An in vitro Study

Angelo‐Khattar

Ibrahim³

et al. 1989

Med Principles Pract

The maternal-fetal transfer of labetalol, an antihypertensive agent, was investigated in vitro, using dual perfusion of isolated human placental lobules with buffered oxygenated Earle’s salt solution as the perfusate. The transport of antipyrine was studied simultaneously to serve as comparison. In 6 experiments, the labetalol transport represented 0.32 ± 0.03 of antipyrine transport fraction. The placental retention of labetalol at steady state represented 2.27 ± 0.51 times the antipyrine retention. The relatively low labetalol transfer, despite its small molecular weight, may be attributed to its high degree of ionization at physiological pH. This observation agrees with earlier studies that ionization is a predominant factor in limiting the placental transfer of drugs.

“…After selecting a cotyledon with maternal surface intact, the corresponding cotyledonary artery and vein were cannulaled and perfused [6,7,[10][11][12]. Per fusion of the maternal side was then done using two microcannulas introduced directly into the intervil lous space by puncturing the basal plate bleached by the fetal side washout.…”

Section: Methodsmentioning

confidence: 99%

Clearance and Disposition of Urea in the Perfused Human Placenta

Kasrawi²,

Al-Bustari

et al. 1989

Med Princ Pract

Urea clearance and disposition is studied in perfused human placenta in vitro using a novel perfusion technique of isolated placental lobules. The results on urea clearance compare well with published reports. The study shows the suitability of urea as a reference marker in placental perfusion studies. It is concluded that urea could serve as an effective reference marker in preference to antipyrine in clearance studies of molecules with membrane-limited transfer.