Arginine Vasopressin-Induced Changes in Blood Flow to the Ovine Chorion,Amnion,and Placenta Across Gestation

Abstract

Objectives: To determine whether physiological increases in fetal plasma arginine vasopressin (AVP) concentration alter blood flow rates to the ovine chorion, amnion or placenta, and to determine whether these AVP-induced changes in flow are dependent on gestational age.

Methods: Colored microspheres (15.10 ± 0.02 μm (standard deviation)) were infused into the superior vena cava before and at 30, 75, and 125 minutes of an intravenous AVP infusion (3 ng/min/kg) in 9 chronically catheterized fetal sheep between 103 to 141 days gestation (term = 147 days). Chorion, amnion, and placental cotyledons were removed, and microspheres were counted to determine blood flow rates.

Results: Fetal arterial pressure (FAP) increased (analysis of variance, P < .0001) and heart rate (FHR) decreased (P < .0001) during the infusion, with responses greater in older (> 125 days) compared to younger (<125 days) fetuses (P < .001). Chorionic blood floow rate increased by 19 ± 7% at 30 min of the AVP infusion, and declined by 18 ± 6% at 75 min, and 32 ± 5% at 125 min (P < .0001). Similarly, fetal placental blood flow rate increased by 20 ± 7% at 30 min of infusion, and declined, in parallel with chorionic blood flow rates, by 6 ± 4% at 75 min, and 17 ± 4% at 125 min (P < .0001). Amniotic blood flow rate did not change significantly during the infusion. The membranous and placental blood flow rate responses to AVP infusion did not depend upon gestational age.

Conclusions: Physiologic increases in plasma AVP concentration induce an early increase in chorionic blood flow followed by a gradual decrease which parallels similar changes in placental blood flow rate. Unlike FAP and FHR, these blood flow changes are not gestational age-dependent. AVP-induced blood flow changes could play an important role in determining abnormalities amniotic fluid volume observed clinically in some stressed fetuses.

Keywords

Membranes fetus arginine vasopressin amniotic fluid volume intramembranous pathway

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References

1. Alexander DP , Bashore RA , Britton HG , Forsling ML . Maternal and fetal arginine vasopressin in the chronically catheterized sheep. Biol Neonate 1974;25:242-248.

2. Rurak DW . Plasma vasopressin levels during hypoxaemia and the cardiovascular effects of exogenous vasopressin in the foetal and adult sheep. J Physiol 1978;277:341-357.

3. Daniel SS , Husian MK , Milliez J , Stark RI , Yeh MN , James LS . Renal response of fetal lamb to complete occlusion of umbilical cord. Am J Obstet Gynecol 1978;131:514-519.

4. Wintour EM , Congiu M , Hardy KJ , Hennessy DP . Regulation of urine osmolality in fetal sheep. Q J Exp Physiol 1982;67:427-435.

5. Tomita H , Brace RA , Cheung CY , Longo LD . Vasopressin dose-response effects on fetal vascular pressures, heart rate and blood volume. Am J Physiol 1985;249:H974-H980.

6. Gilbert WM , Cheung CY , Brace RA . Rapid intramembranous absorption into the fetal circulation of arginine vasopressin injected intraamniotically. Am J Gynecol 1991;164:1013-1020.

7. Stark RI , Daniel SS , Husain MK , Sanocka UM , Zybrow AB , James LS . Vasopressin in amniotic fluid as an index of fetal hypoxia: mechanism of release in sheep. Pediatr Res 1984;18:835-841.

8. Brace RA . Progress toward understanding the regulation of amniotic fluid volume: water and solute fluxejs in and through the fetal extraplacental membranes. Placenta 1995;16:1-18.

9. Brace RA , Gilbert WM , Thornburg KL . Vascularization of the ovine amnion and chorion: A morphometric characterization of the surface area of the intramembranous pathway. Am J Obstet Gynecol 1992;167:1747-1755.

10.

10. Hedriana HL , Brace RA , Gilbert WM . Changes in blood flow to the ovine chorion and amnion across gestation. J Soc Gynecol Invest 1995;2:727-734.

11.

11. Makowski EL , Meschia G , Droegemueller W , Battaglia FC . Measurement of umbilical arterial blood flow to the sheep placenta and fetus in utero: Distribution to cotyledons and intercotyledonary chorion. Circ Res 1968;23:623-631.

12.

12. Lumbers ER , Kingsford NM , Menzies RI , Stevens AD . Acute effects of captopril, an angiotensin-converting enzyme inhibitor, on the pregnant ewe and fetus. Am J Physiol 1992;262:R754-R760.

13.

13. Gibson KJ , Lumbers ER . The roles of arginine vasopressin in fetal sodium balance and as a mediator of the effects of fetal “stress.” J Dev Physiol 1993;19:125-136.

14.

14. Lumbers ER , Smith FG , Stevens AD . Measurement of net transplacental transfer of fluid to the fetal sheep. J Physiol 1985;364:289-299.

15.

15. Iwamoto HS , Rudolph AM , Keil LC , Heyman MA . Hemodynamic responses of the sheep fetus to vasopressin infusion. Circ Res 1979;44:430-436.

16.

16. Paulick RP , Meyers RL , Rudolph CD , Rudolph AM . Umbilical and hepatic venous responses to circulating vasoconstrictive hormones in fetal lamb. Am J Physiol 1991;260:H1205-H1213.

17.

17. Irion GL , Mack CE , Clark KE . Fetal hemodynamic and fetoplacental vascular response to exogenous arginine vasopressin. Am J Obstet Gynecol 1990;62:1115-1120.

18.

18. Wiriyathian S , Porter JC , Nader RP , Rosenfeld CR . Cardiovascular effects and clearance of arginine vasopressin in the fetal lamb. Am J Physiol 1983;245:E24-E31.

19.

19. Gibson KJ , Lumbers ER . Ovine fetal cardiovascular, renal, and fluid balance responses to 3 days of high arginine vasopressin levels. Am J Physiol 1997;272:R1069-R1076.

20.

20. Dawes GS . Fetal and neonatal physiology: A comparative study of the changes at birth. Chicago: Year Book Medical Publishers, Inc., 1968.

21.

21. Zhang S , Hirano Y , Hiraoka M . Arginine vasopressin-induced potentiation of unitary L-type Ca2+ channel current in guinea pig ventricular myocytes. Circ Res 1995;76:592-599.