Angiotensin II and alpha-agonist. I. Responses of ovine fetoplacental vasculature

1990 ◽  
Vol 259 (2) ◽  
pp. H464-H472 ◽  
Author(s):  
T. Yoshimura ◽  
R. R. Magness ◽  
C. R. Rosenfeld
Keyword(s):  
Blood Flow ◽  
Angiotensin Ii ◽  
Vascular Resistance ◽  
Plasma Catecholamines ◽  
Ang Ii ◽  
Adrenergic Stimulation ◽  
Umbilical Blood ◽  
Steady State Responses ◽  
Maternal Responses ◽  
Dose Dependent

During ovine pregnancy the uteroplacental vasculature is less responsive to angiotensin II (ANG II)-induced vasoconstriction than the systemic vasculature, whereas responses to alpha-agonists are just the opposite. Comparisons of fetal systemic and placental vascular responses to these agents are not well described, nor have they been compared with maternal responses. We determined steady-state responses to fetal infusions (5-7 min) of ANG II (0.023-5.73 micrograms/min) and phenylephrine (PHEN, 0.031-7.64 micrograms/min), continuously monitoring mean arterial pressure (MAP), heart rate (HR), and umbilical blood flow (UmBF). Although both vasoconstrictors caused dose-dependent increases in MAP and umbilical vascular resistance (UmVR), responsiveness (delta MAP and delta UmVR) to ANG II (mol/min) was 35- to 60-fold greater than to PHEN. ANG II caused dose-dependent decreases in UmBF (2-48%); PHEN had minimal effects except at the highest dose, UmBF decreasing only 18%. Although patterns of fetal responses of MAP, UmBF, and UmVR to ANG II resembled maternal responses of MAP and uterine blood flow and uterine vascular resistance, the former were greatly attenuated. Similar observations were made with PHEN for UmBF and UmVR but not MAP. ANG II is a more potent fetal systemic and placental vasoconstrictor than PHEN; however, compared with those of the mother the responses are attenuated. Moreover, the fetoplacental vascular bed appears unresponsive to alpha-adrenergic stimulation, possibly reflecting a mechanism for maintaining UmBF when plasma catecholamines are elevated.

Uterine and nonuterine vascular responses to angiotensin II in ovine pregnancy

1989 ◽  
Vol 257 (1) ◽  
pp. H17-H24 ◽  
Author(s):  
C. R. Rosenfeld ◽  
R. P. Naden
Keyword(s):  
Blood Flow ◽  
Angiotensin Ii ◽  
Vascular Resistance ◽  
Ang Ii ◽  
Uterine Blood Flow ◽  
Blood Flows ◽  
Pregnant Sheep ◽  
Regional Blood Flows ◽  
Dose Dependent ◽  
Systemic Responses

The uteroplacental vasculature is more refractory to angiotensin II (ANG II) than the systemic vasculature as a whole. To ascertain the differences in responses between reproductive and nonreproductive tissues that account for this, we infused ANG II (0.573, 5.73, and 11.5 micrograms/min) in pregnant sheep (137 +/- 5 days of gestation) and monitored arterial pressure (MAP), heart rate, and uterine blood flow (UBF); cardiac output and regional blood flows were measured with radiolabeled microspheres. Dose-dependent changes in MAP, UBF, and systemic (SVR) and uterine (UVR) vascular resistance occurred (P less than 0.05); systemic responses exceeded uterine (P less than 0.05), except with 11.5 micrograms/min, when % delta UVR = % delta SVR, % delta UVR greater than % delta MAP, and UBF fell 29%. Although a dose-dependent rise in placental resistance occurred, blood flow was unaffected except at 11.5 micrograms ANG II/min, falling 16.8 +/- 3.5% (P = 0.059). In contrast, endometrial perfusion decreased 68 +/- 4.2 and 81 +/- 1.8% (P less than 0.01) with 5.73 and 11.5 micrograms ANG II/min, respectively. Myometrial responses were intermediate, thus placental flow increased from 75 to greater than 90% of total UBF. Adipose, renal, and adrenal glands were extremely sensitive to ANG II, with blood flows decreasing maximally at 0.573 micrograms/min (P less than 0.05). Maximum adipose vascular resistance occurred at 0.573 micrograms/min, greater than 400% (P less than 0.001), exceeding responses in all tissues (P less than 0.05). The placenta is less responsive to ANG II than other uterine and most nonreproductive tissues, resulting in preferential maintenance of uteroplacental perfusion and protecting the fetus from the effects of this vasoconstrictor.

Differential responses of uterine and umbilical vasculatures to angiotensin II and norepinephrine

1990 ◽  
Vol 259 (1) ◽  
pp. H197-H203 ◽  
Author(s):  
K. E. Clark ◽  
G. L. Irion ◽  
C. E. Mack
Keyword(s):  
Blood Flow ◽  
Angiotensin Ii ◽  
Arterial Pressure ◽  
Vascular Resistance ◽  
Base Line ◽  
Ang Ii ◽  
Uterine Blood Flow ◽  
Umbilical Blood ◽  
Arterial Blood ◽  
Pregnant Sheep

Although the uterine vascular responses to endogenous vasoactive substances have been extensively investigated in pregnant sheep, the fetal umbilical responses to angiotensin II (ANG II) and norepinephrine (NE) have not been well characterized. Twenty-five pregnant ewes between 105 and 115 days of gestation were anesthetized and instrumented for hemodynamic measurements, systemic fetal and maternal intravenous infusions, and local maternal uterine arterial infusions of ANG II and NE. Fetal and maternal arterial pressure and heart rate, maternal uterine blood flow (total of left and right middle uterine arteries), and fetoplacental blood flow (common umbilical artery) were measured during continuous infusions of ANG II or NE. Fetal infusions of ANG II (0.03–1.0 micrograms.min-1.kg estimated fetal body wt-1) increased fetal arterial blood pressure by as much as 44% over base-line values, decreased umbilical blood flow by as much as 63%, and increased umbilical vascular resistance by up to 345%. Fetal infusions of NE (0.1–3 micrograms.min-1.kg-1) increased fetal arterial pressure 42% and increased umbilical vascular resistance by up to 38% but did not significantly alter fetoplacental blood flow. No significant maternal changes were observed during fetal infusions. Maternal infusion of ANG II increased maternal arterial pressure by as much as 59% and significantly increased uterine vascular resistance at the two highest doses but significantly decreased uterine blood flow only at the highest dose (17%; P less than 0.05). Maternal infusions of NE increased arterial pressure by as much as 113%, decreased uterine blood flow by as much as 76%, and increased uterine vascular resistance 3- to 10-fold over the base-line value.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential development of umbilical and systemic arteries. I. ANG II receptor subtype expression

1998 ◽  
Vol 274 (3) ◽  
pp. R797-R807 ◽  
Author(s):  
Jeffrey R. Kaiser ◽  
Blair E. Cox ◽  
Timothy A. Roy ◽  
Charles R. Rosenfeld
Keyword(s):  
Blood Flow ◽  
Radioligand Binding ◽  
Plasma Renin ◽  
Receptor Subtype ◽  
Ang Ii ◽  
Binding Assays ◽  
Fetal Sheep ◽  
Umbilical Blood ◽  
Steady State Responses ◽  
Umbilical Arteries

In fetal sheep umbilical responses to angiotensin II (ANG II) exceed those by systemic vasculature. Two ANG II receptors (AT) exist, AT1 and AT2, but only AT1 mediates vasoconstriction in adult tissues. Thus differences in reactivity could reflect differences in subtype expression. Using competitive radioligand binding assays, we demonstrated AT1 predominance in umbilical arteries and AT2 in femoral arteries. Steady-state responses to intravenous ANG II (0.229–1.72 μg/min) were studied in 16 fetuses with umbilical and/or femoral artery flow probes without and with local AT1 (L-158,809) or AT2 (PD-123319) blockade. ANG II dose dependently ( P < 0.001) increased umbilical resistance more than arterial pressure (MAP) while decreasing umbilical blood flow. Femoral vascular resistance also increased dose dependently ( P = 0.02), but responses were less than umbilical ( P = 0.0001) and paralleled increases in MAP; blood flow was unaffected. Cumulative local doses of L-158,809 (125 μg) inhibited all responses ( P< 0.001); however, 1,000 μg of the AT2 antagonist had no effect. Plasma renin activity (PRA) was unaltered by local AT1 blockade, whereas PRA doubled ( P = 0.001) after systemic infusion of only 50 μg of the AT1 antagonist and remained elevated. Differences in umbilical and femoral vascular responses to ANG II are in large part due to differences in AT subtype expression. Furthermore, in fetal sheep the ANG II negative feedback on PRA is mediated by AT1 receptors, and it is substantially more sensitive to receptor blockade than the vasculature.

Fetal placental vascular responses to prostacyclin after angiotensin II-induced vasoconstriction

1989 ◽  
Vol 257 (1) ◽  
pp. E102-E107
Author(s):  
V. M. Parisi ◽  
S. W. Walsh
Keyword(s):  
Blood Flow ◽  
Angiotensin Ii ◽  
Vascular Resistance ◽  
Control Period ◽  
Vena Cava ◽  
Ang Ii ◽  
Flow Measurements ◽  
Control Value ◽  
Blood Flow Measurements ◽  
Infusion Period

The vasodilator prostacyclin is produced by many fetal tissues and may serve to protect umbilical placental blood flow. We hypothesized that prostacyclin could reverse fetoplacental vasoconstriction produced by angiotensin II (ANG II). Studies were done in eight unanesthetized near-term ovine fetuses. After a control period, ANG II was infused into the fetal inferior vena cava at a rate of 0.5 microgram/min for 40 min. Twenty minutes after starting the ANG II infusion, an infusion of prostacyclin at a rate of 5 micrograms/min was added to the ANG II infusion. Blood flows were measured by the radioactive microsphere technique. Blood flow measurements were made during the control period, 20 min after starting the ANG II infusion, and 20 min after adding prostacyclin to the ANG II infusion. ANG II produced significant fetal hypertension and renal, intestinal, and placental vasoconstriction. Placental vascular resistance rose from 0.14 +/- 0.01 to 0.18 +/- 0.01 mmHg.min.kg fetal wt.ml-1 during the ANG II infusion period (P less than 0.05). The addition of prostacyclin to the ANG II infusion resulted in a return to control values for fetal blood pressure and renal and intestinal resistance. However, placental vasoconstriction was not reversed by addition of prostacyclin as placental vascular resistance remained significantly elevated over the control value (0.17 +/- 0.01 mmHg.min.kg fetal wt.ml-1). Although unchanged by ANG II infusion, fetal pH decreased significantly during the ANG II plus prostacyclin infusion period. We conclude that ANG II causes fetal hypertension and renal and intestinal vasoconstriction, which are reversed by prostacyclin.(ABSTRACT TRUNCATED AT 250 WORDS)

Combined effects of autoregulation and vasoconstrictors on hindquarters vascular resistance

1990 ◽  
Vol 258 (4) ◽  
pp. H1032-H1041 ◽  
Author(s):  
G. A. Meininger ◽  
J. P. Trzeciakowski
Keyword(s):  
Blood Flow ◽  
Vascular Resistance ◽  
Dose Response ◽  
Perfusion Pressure ◽  
Combined Effects ◽  
Ang Ii ◽  
Response Curves ◽  
Local Pressure ◽  
Pressure Flow ◽  
Dose Dependent

Relative contributions of local autoregulatory tone and vasoconstrictor tone to skeletal muscle vascular resistance were studied in anesthetized rats during hypertension produced by vasoconstrictor infusion. Rats were instrumented with a Doppler flow probe on the sacral aorta (SA) to measure blood flow and to allow calculation of vascular resistance. An occluder was placed on the SA and used to produce stepwise reductions in local perfusion pressure. Pressure-flow curves for the hindquarters were obtained in the absence and presence of elevated mean arterial pressure (MAP) produced by infusion of angiotensin II (ANG II; 50-1,247 ng.kg-1.min-1) or phenylephrine (PE; 2.5-12.4 micrograms.kg-1.min-1). Both ANG II and PE infusion increased MAP. For example, MAP was increased by ANG II from 91 to 134 mmHg and by PE from 89 to 156 mmHg. In addition, infusions of ANG II and PE produced dose-dependent rightward shifts in the hindquarters pressure-flow relationship. To examine the effect of pressure on the dose-response relationships of ANG II or PE, local perfusion pressure was adjusted to remain constant at various pressure levels that were independent of MAP during drug infusions. This produced a series of distinct dose-response curves with each curve defined by a different pressure level and with each characterized by a different maximum change in vascular resistance. If local perfusion pressure was not held constant but was permitted to increase with MAP, a compound dose-response curve was obtained in which the combined effects of the change in local pressure (i.e., autoregulation) and vasoconstrictor dose on vascular resistance could be discerned. These data demonstrate that hindquarters blood flow autoregulation continues to occur in the presence of vasoconstrictors. Consequently, autoregulatory mechanisms may be stimulated by any increase in MAP whether associated with systemic vasoconstrictor infusion or activation of neurohumoral pressor systems. The result is an amplified rise in local vascular resistance.

Umbilical and hepatic venous responses to circulating vasoconstrictive hormones in fetal lamb

1991 ◽  
Vol 260 (4) ◽  
pp. H1205-H1213 ◽  
Author(s):  
R. P. Paulick ◽  
R. L. Meyers ◽  
C. D. Rudolph ◽  
A. M. Rudolph
Keyword(s):  
Blood Flow ◽  
Angiotensin Ii ◽  
Vascular Resistance ◽  
Ductus Venosus ◽  
Dependent Manner ◽  
Outflow Resistance ◽  
Fetal Sheep ◽  
Descending Aorta ◽  
Placental Blood ◽  
Dose Dependent

Acute fetal hypoxemia increases the vascular resistance of the umbilical veins as well as that of the liver. Because, at least in the human, the umbilical-placental circulation has no autonomic innervation, circulating hormones could well be responsible for this increase in umbilical-placental outflow resistance. In chronically instrumented fetal sheep, norepinephrine, epinephrine, vasopressin, and angiotensin II were infused in sequentially increasing doses into the descending aorta and vascular resistance to umbilical-placental blood flow was measured. Norepinephrine and epinephrine increased the vascular resistance of the umbilical veins in a dose-dependent manner. Both catecholamines also increased the vascular resistance of the liver, resulting in an increase in ductus venosus blood flow. In contrast, vasopressin and angiotensin II had no effect on umbilical-placental outflow resistance. Thus catecholamines may be responsible for the increase in the vascular resistance of the umbilical veins and liver in response to acute fetal hypoxemia.

Cardiovascular effects of angiotensin-II-mediated adrenaline release in rainbow trout Oncorhynchus mykiss

1999 ◽  
Vol 202 (1) ◽  
pp. 55-66 ◽  
Author(s):  
N.J. Bernier ◽  
S.F. Perry
Keyword(s):  
Angiotensin Ii ◽  
Plasma Catecholamines ◽  
Cardiovascular Effects ◽  
Systemic Resistance ◽  
Plasma Catecholamine ◽  
Dependent Manner ◽  
Ang Ii ◽  
Plasma Adrenaline ◽  
Alpha Adrenoceptor ◽  
Dose Dependent

To determine the contribution of plasma catecholamines to the cardiovascular effects of elevated levels of angiotensin II (Ang II) in trout, this study investigated (1) the stimulatory effects of [Asn1-Val5]-Ang II on plasma catecholamine levels, (2) the cardiovascular effects of Ang II with and without alpha-adrenoceptor blockade and (3) the relationship between plasma adrenaline concentrations and their cardiovascular effects. Bolus intravascular injections of Ang II (25–1200 pmol kg-1) elicited dose-dependent (between 75 and 1200 pmol kg-1) increases in plasma adrenaline levels; mean plasma noradrenaline levels only increased in response to a dose of 1200 pmol kg-1. Ang-II-elicited increases in plasma adrenaline levels ranged from 3.3+/−0.3 nmol l-1 for 75 pmol kg-1 Ang II to 125.1+/−40.0 nmol l-1 for 1200 pmol kg-1 Ang II. Injections of Ang II (25–1200 pmol kg-1) also elicited dose-dependent increases in dorsal aortic pressure (PDA), systemic resistance (RS), cardiac output (Q) and stroke volume (Vs). In fish first treated with the alpha -adrenoceptor blocker phenoxybenzamine, Ang II injections elicited a decrease in q_dot and Vs, and the increases in PDA and RS following administration of the 600 and 1200 pmol kg-1 Ang II doses were significantly reduced. Bolus injections of adrenaline (1.8×10(−10) to 1.4×10(−8) mol kg-1) elicited dose-dependent increases in PDA at a plasma adrenaline concentration of 16.5 nmol l-1 and in RS at a plasma adrenaline concentration of 50.5 nmol l-1. Adrenaline injections also elicited increases in Q and Vs at plasma adrenaline concentrations of 50.5 nmol l-1; however, higher plasma adrenaline concentrations were not associated with further increases in either Q or Vs. These results demonstrate that, in vivo, Ang II can act as a potent non-cholinergic secretagogue of humoral adrenaline in trout and that some of the cardiovascular effects of exogenous Ang II can be attributed to increased levels of plasma adrenaline. Our data also indicate that the cardiovascular effects of Ang-II-mediated humoral catecholamines are recruited in a dose-dependent manner and, as such, may require an acute stimulation of the renin-angiotensin system to contribute significantly to the pressor activity of endogenous angiotensins.

Pulmonary vascular response to angiotensin II in canine pacing-induced heart failure

1996 ◽  
Vol 271 (1) ◽  
pp. H222-H227 ◽  
Author(s):  
B. J. Roy ◽  
V. H. Pitts ◽  
M. I. Townsley
Keyword(s):  
Heart Failure ◽  
Blood Flow ◽  
Angiotensin Ii ◽  
Pulmonary Vascular Resistance ◽  
Vascular Resistance ◽  
Venous Pressure ◽  
Left Ventricular ◽  
Microvascular Permeability ◽  
Ang Ii ◽  
Vascular Response

The effects of angiotensin II(ANG II) on pulmonary vascular resistance and microvascular permeability were studied in isolated, blood-perfused, ventilated canine lung lobes from control animals (n = 40) and animals with pacing-induced heart failure (n = 15). Conditioned dogs were paced (245 beats/min) for 30.6 +/- 0.9 (SE) days until left ventricular shortening fraction decreased by 56% (P < 0.05). Baseline pulmonary arterial resistance (Ra) (19.1 +/- 1.6 vs. 8.0 +/- 1.1 cmH2O.1(-1).min.100g) and venous resistance (Rv) (17.1 +/- 2.3 vs. 7.8 +/- 1.0 cmH2O.1(-1).min.100 g) were greater (P < 0.05) in the paced group compared with controls, respectively. Increments in Ra (delta Ra) and Rv(delta Rv) were measured after intra-arterial boluses of ANG II (1-10 micrograms). ANG II produced a dose-dependent response in delta Ra that was enhanced after pacing (P < 0.05). There was no effect on delta Rv in either group. At increased venous pressure (Pv = 20 cmH2O), the increments in delta Ra were significantly attenuated in both groups. In control lobes at low Pv, delta Ra and delta Rv both tended to decrease with increased lobar blood flow, suggesting that blood flow affects the pulmonary vascular response of ANG II. The baseline capillary filtration coefficient (Kf,c) was not different in the paced group compared with control, nor was there any effect of ANG II on Kf,c in the paced group. However, Kf,c did increase after ANG II in the control groups evaluated at either low or high Pv (P < 0.05). This difference in Kf,c was not seen if the experiment was done at increased Pv but without ANG II administration. We conclude that the pulmonary vasoconstrictor activity of ANG II is modestly enhanced in canine pacing-induced heart failure. Nonetheless, ANG II does not likely contribute to increased pulmonary vascular resistance in vivo in heart failure, since this effect was abolished at increased Pv. Finally, the absence of any effect of ANG II on pulmonary microvascular permeability in the paced group is suggestive of some adaptive remodeling of the capillary endothelial barrier.

Modulation of Ca2+ transients in neonatal and adult rat cardiomyocytes by angiotensin II and endothelin-1

1996 ◽  
Vol 270 (3) ◽  
pp. H857-H868 ◽  
Author(s):  
R. M. Touyz ◽  
J. Fareh ◽  
G. Thibault ◽  
B. Tolloczko ◽  
R. Lariviere ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Receptor Agonist ◽  
Dependent Manner ◽  
Induced Responses ◽  
Ang Ii ◽  
Binding Studies ◽  
Vasoactive Peptides ◽  
Adult Cardiomyocytes ◽  
Etb Receptor ◽  
Dose Dependent

Vasoactive peptides may exert inotropic and chronotropic effects in cardiac muscle by modulating intracellular calcium. This study assesses effects of angiotensin II (ANG II) and endothelin-1 (ET-1) on intracellular free calcium concentration ([Ca2+]i) in cultured cardiomyocytes from neonatal and adult rats. [Ca2+]i was measured microphotometrically and by digital imaging using fura 2 methodology. Receptor subtypes through which these agonists induce responses were determined pharmacologically and by radioligand binding studies. ANG II and ET-1 increased neonatal atrial and ventricular cell [Ca2+]i transients in a dose-dependent manner. ANG II (10(-11) to 10(-7) M) failed to elicit [Ca2+]i responses in adult cardiomyocytes, whereas ET-1 increased [Ca2+]i in a dose-dependent manner. The ETA receptor antagonist BQ-123 significantly reduced (P 7< 0.05) ET-1 induced responses, and the ETB receptor agonist IRL-1620 (10(-7) to 10(-5) M) significantly increased (P < 0.05) [Ca2+]i in neonatal and adult cardiomyocytes. ET-1 binding studies demonstrated 85% displacement by BQ-123 and approximately 15% by the ETB receptor agonist sarafotoxin S6c, suggesting a predominance of ETA receptors. Competition binding studies for ANG II failed to demonstrate significant binding on adult ventricular myocytes, indicating the absence or presence of very few ANG II receptors. These data demonstrate that ANG II and ET-1 have stimulatory [Ca2+]i effects on neonatal cardiomyocytes, whereas in adult cardiomyocytes, ANG II-induced effects are insignificant, and only ET-1-induced responses, which are mediated predominantly via ETA receptors, are preserved. Cardiomyocyte responses to vasoactive peptides may thus vary with cardiac development.

Angiotensin II induces insulin resistance independent of changes in interstitial insulin

1999 ◽  
Vol 277 (5) ◽  
pp. E920-E926 ◽  
Author(s):  
Joyce M. Richey ◽  
Marilyn Ader ◽  
Donna Moore ◽  
Richard N. Bergman
Keyword(s):  
Insulin Resistance ◽  
Heart Rate ◽  
Blood Flow ◽  
Angiotensin Ii ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Glucose Uptake ◽  
Peripheral Resistance ◽  
Glucose Turnover ◽  
Ang Ii

We set out to examine whether angiotensin-driven hypertension can alter insulin action and whether these changes are reflected as changes in interstitial insulin (the signal to which insulin-sensitive cells respond to increase glucose uptake). To this end, we measured hemodynamic parameters, glucose turnover, and insulin dynamics in both plasma and interstitial fluid (lymph) during hyperinsulinemic euglycemic clamps in anesthetized dogs, with or without simultaneous infusions of angiotensin II (ANG II). Hyperinsulinemia per se failed to alter mean arterial pressure, heart rate, or femoral blood flow. ANG II infusion resulted in increased mean arterial pressure (68 ± 16 to 94 ± 14 mmHg, P < 0.001) with a compensatory decrease in heart rate (110 ± 7 vs. 86 ± 4 mmHg, P < 0.05). Peripheral resistance was significantly increased by ANG II from 0.434 to 0.507 mmHg ⋅ ml−1⋅ min ( P < 0.05). ANG II infusion increased femoral artery blood flow (176 ± 4 to 187 ± 5 ml/min, P < 0.05) and resulted in additional increases in both plasma and lymph insulin (93 ± 20 to 122 ± 13 μU/ml and 30 ± 4 to 45 ± 8 μU/ml, P < 0.05). However, glucose uptake was not significantly altered and actually had a tendency to be lower (5.9 ± 1.2 vs. 5.4 ± 0.7 mg ⋅ kg−1⋅ min−1, P > 0.10). Mimicking of the ANG II-induced hyperinsulinemia resulted in an additional increase in glucose uptake. These data imply that ANG II induces insulin resistance by an effect independent of a reduction in interstitial insulin.

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