Dynamics of uterine circulation in pregnant and nonpregnant sheep

Ladner, C.; Brinkman, C.R.; Weston, Peter V.; Assali, N.S.

doi:10.1152/ajplegacy.1970.218.1.257

Cited by 100 publications

(35 citation statements)

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“…The magnitude of oestrogen-induced vasodilatation in chronic preparations is clearly much greater in ovariectomized (Killam et al, 1973;Resnik, Killam, Battaglia, Makowski & Meschia, 1974;Resnik, Battaglia, Makowski & Meschia, 1975;Resnik & Brink, 1978, 1980 than in intact animals (Nuwayhid et al, 1975;present results), probably due to differences in tissue sensitivity resulting from endogenous steroid depletion and subsequent stimulation by repeated injections of oestradiol. Thus, the high flow observed in our study in pregnant animals cannot be attributed to anaesthesia, though it may be related to a reduction in sympathetic vascular tone arising from the procedure of confining flow to the middle uterine artery (Ladner, Brinkman, Weston & Assali, 1970;Bell, 1972). This procedure may also result in a redistribution of the arterial supply to the pregnant uterus if blood flow through the middle uterine artery is normally supplemented by that of the caudal uterine artery.…”

Section: Discussionmentioning

confidence: 70%

Uterine blood flow, myometrial activity and their response to adenosine during the peri-implantation period in sheep

Fleet¹,

Heap²

1982

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Summary. Uterine blood flow and myometrial activity were measured simultaneously in anaesthetized sheep 15 days after a sterile (non-pregnant group) or fertile (pregnant) mating. During the peri-implantation period uterine blood flow was similar in both groups of animals, but spontaneous myometrial activity was greatly reduced in pregnant ewes. This 'block' of myometrial activity was associated with circulating levels of progesterone which were significantly higher (2\m=.\8\ m=+-\0\m=.\8ng/ml, mean \m=+-\ s.e.m.) than those in non-pregnant animals (0\m=.\4 \m=+-\0\m=.\3 ng/ml). Adenosine injected into the uterine artery produced uterine vasodilatation in both groups, but the log dose\p=n-\response was significantly less in pregnant than in non-pregnant animals (P < 0\m=.\001).Myometrial activity was stimulated by adenosine, particularly in the pregnant group (P < 0\m=.\001

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Section: Discussionmentioning

confidence: 70%

Uterine blood flow, myometrial activity and their response to adenosine during the peri-implantation period in sheep

Fleet¹,

Heap²

1982

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“…Previous studies in pregnant ewes have sugDr. Venuto Received for publication 24 July 1975 and in revised form 3 December 1975. gested failure of the uterine circulation to regulate flow; as if the uterine vascular bed acted like a series of rigid tubes, flow being proportional to perfusion pressure (1,2). If the uterine circulation of the human behaves similarly, there would be important clinical implications in the development of hypertension and its treatment during pregnancy.…”

Section: Introductionmentioning

confidence: 99%

The effect of changes in perfusion pressure on uteroplacental blood flow in the pregnant rabbit.

Venuto¹,

Cox²,

Stein³

et al. 1976

J. Clin. Invest.

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A B S T R A C T The effect of perfusion pressure on uteroplacental blood flow was determined in pregnant rabbits utilizing the radioactive microsphere method.Control mean arterial pressure, 93 mm Hg±2.6 SEM, was raised by carotid ligation to 109±4.1 mm Hg and then reduced with antihypertensive drugs to 74+1.3 mm Hg. Over this range of pressure there was no significant change in cardiac output, 605+36, 523+37, and 540±39 ml/min; or uteroplacental blood flow, 30+3.2, 27±5.2, and 29±4.5 ml/min, respectively. When prostaglandin synthesis was inhibited with either indomethacin or meclofenamate (2 mg/kg), uterine vascular resistance was higher but maintenance of uteroplacental flow occurred over a perfusion pressure of 89±6.7-115 +9.3 mm Hg. With more severe hypotension induced with trimethaphan, control arterial pressure fell from 92±2.4 to 39+0.9 mm Hg, cardiac output fell from 514 +17 to 407+22 ml/min (P < 0.025) and uteroplacental blood flow fell from 6.1±0.9 to 2.5±0.9% of cardiac output (P<0.05), which represented an absolute fall from 32.4±5 to 10.6±3 ml/min (P <0.025). There was no significant change in renal blood flow expressed as percentage of cardiac output, 14.9+2 and 13±1.5%, or in absolute flow, 75+77 and 54+7 ml/min with trimethaphan-induced hypotension.These studies indicate that uteroplacental blood flow is maintained relatively constant over a range of perfusion pressure of 60-140 mm Hg in both normal and prostaglandin-inhibited pregnant rabbits. However, with reduction in pressure to 36-42 mm Hg, uteroplacental blood flow falls, expressed as a percentage of cardiac output and in absolute flow.

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“…There have been reports of both decreases (1)(2)(3) and increases (4)(5)(6)(7)(8)(9)(10)(11) in uteroplacental blood flow (UBF).1 This has resulted in the conflicting conclusions that angiotensin II acts either as a uterine vasoconstrictor, as in other vascular beds, or as if it has a paradoxical and "unique" vasodilator action on the uterine vasculature (5). This is an important issue in view ofevidence that renin is produced in the pregnant uterus of several species including the human (12), and that in the pregnant rabbit, uterine renin release is increased under conditions of uterine hypoperfusion (5).…”

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confidence: 99%

“…No animal was stLdied until at least day 6 after surgery. Two studies were carried out on each animal 2-6 d apart.…”

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confidence: 99%

Effect of angiotensin II on uterine and systemic vasculature in pregnant sheep.

Naden¹,

Rosenfeld²

1981

J. Clin. Invest.

101

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Dynamics of uterine circulation in pregnant and nonpregnant sheep

Cited by 100 publications

References 0 publications

Uterine blood flow, myometrial activity and their response to adenosine during the peri-implantation period in sheep

Uterine blood flow, myometrial activity and their response to adenosine during the peri-implantation period in sheep

The effect of changes in perfusion pressure on uteroplacental blood flow in the pregnant rabbit.

Effect of angiotensin II on uterine and systemic vasculature in pregnant sheep.

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