Vascular pressure-volume relationships in pregnant and estrogen-treated guinea pigs.
We investigated the relationship between mean circulatory filling pressure (MCFP) and blood volume in nonpregnant (NP), estrogen-treated (E), and pregnant (P) guinea pigs. Reversible circulatory arrest was produced by rapid ventricular pacing or acetylcholine in unanesthetized animals remote from surgery. MCFP (mmHg) was higher for E (7.1 +/- 0.3) than for NP (5.8 +/- 0.5) or P (5.3 +/- 0.4). The gradient for venous return, the difference between MCFP and right atrial pressure (mmHg), did not differ in NP- (6.0 +/- 0.5), P- (5.8 +/- 0.5), or E- (5.8 +/- 0.4) treated animals. Capacitance, the blood volume (ml/kg) at an MCFP of 6 mmHg, was increased in P (84 +/- 6) and E (89 +/- 7), compared with NP (64 +/- 5) animals. Compliance, the ratio of the change in volume to change in pressure in the range of 6-12 mmHg (ml.kg-1.mmHg-1), was greater in P (4.4 +/- 0.3) than NP (3.5 +/- 0.3) animals. Hexamethonium blockade did not affect MCFP, capacitance, or compliance. We conclude that the effect of blood volume expansion on the circulation in pregnancy cannot be predicted from knowledge of MCFP-blood volume relationships in the nonpregnant animal, because capacitance and compliance are altered. Estrogen administration to nonpregnant animals reproduces some of these effects.
Davis
L E
LE
Department of Obstetrics and Gynecology, Oregon Health Sciences University, Portland 97201-3098.
Hohimer
A R
AR
Giraud
G D
GD
Paul
M S
MS
Morton
M J
MJ
D000818:Animals; D001775:Blood Circulation; D001794:Blood Pressure; D001810:Blood Volume; D003911:Dextrans; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D005730:Ganglionic Blockers / Q000494:pharmacology; D006168:Guinea Pigs; D006325:Heart Atria; D006439:Hemodynamics / Q000187:drug effects; D018738:Hexamethonium; D006584:Hexamethonium Compounds / Q000494:pharmacology; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*
D003911:Dextrans; D005730:Ganglionic Blockers; D006584:Hexamethonium Compounds; D018738:Hexamethonium; D004958:Estradiol