Ultradian adrenocortical and circulatory oscillations in conscious dogs

1990 ◽  
Vol 258 (3) ◽  
pp. R578-R590 ◽  
Author(s):  
L. A. Benton ◽  
F. E. Yates
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Venous Blood ◽  
Time History ◽  
Secretion Rate ◽  
Conscious Dogs ◽  
Cortisol Secretion ◽  
Arterial Blood ◽  
Tightly Coupled ◽  
Adrenal Glucocorticoid

We examined adrenal blood flow, cortisol secretion rate, concentration of cortisol in adrenal venous blood, mean arterial blood pressure, and heart rate in unrestrained conscious dogs, sampling at 15-20 s, 5 min, or 10 min during experiments lasting from 30 min to 8 h. Time history analysis designed for short, noisy time series detected three significant ultradian oscillatory periods: approximately 3, 6, and 90 min. Circulatory variables (systemic mean arterial pressure, heart rate, and adrenal blood flow) showed all three. Cortisol secretion rate showed the 3- and 90-min oscillations but not the 6-min oscillation. Adrenal glucocorticoid secretion rate and adrenal blood flow were not strongly coupled. However, at one extreme of blood flow (close to zero) and at the opposite extreme (very high blood flow stimulated by adrenocorticotropic hormone) adrenal blood flow and cortisol secretion were tightly coupled. In the normal physiological range, the multiperiodic, rhythmic organization of circulatory variables and adrenal glucocorticoid function arises from independent or only weakly coupled oscillators, not necessarily harmonically related, manifesting near-periodicity with wobble and intermittency.

Effects of l-arginine on systemic and renal haemodynamics in conscious dogs

1991 ◽  
Vol 81 (6) ◽  
pp. 727-732 ◽  
Author(s):  
Marohito Murakami ◽  
Hiromichi Suzuki ◽  
Atsuhiro Ichihara ◽  
Mareo Naitoh ◽  
Hidetomo Nakamoto ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Renal Blood Flow ◽  
Arterial Blood Pressure ◽  
Mean Arterial Blood Pressure ◽  
Renal Haemodynamics ◽  
Conscious Dogs ◽  
Arginine Infusion ◽  
Arterial Blood

1. The effects of l-arginine on systemic and renal haemodynamics were investigated in conscious dogs. l-Arginine was administered intravenously at doses of 15 and 75 μmol min−1 kg−1 for 20 min. 2. Mean arterial blood pressure, heart rate and cardiac output were not changed significantly by l-arginine infusion. However, l-arginine infusion induced a significant elevation of renal blood flow from 50 ± 3 to 94 ± 12 ml/min (means ± sem, P < 0.01). 3. Simultaneous infusion of NG-monomethyl-l-arginine (0.5 μmol min−1 kg−1) significantly inhibited the increase in renal blood flow produced by l-arginine (15 μmol min−1 kg−1) without significant changes in mean arterial blood pressure or heart rate. 4. Pretreatment with atropine completely inhibited the l-arginine-induced increase in renal blood flow, whereas pretreatment with indomethacin attenuated it (63 ± 4 versus 82 ± 10 ml/min, P < 0.05). 5. A continuous infusion of l-arginine increased renal blood flow in the intact kidney (55 ± 3 versus 85 ± 9 ml/min, P < 0.05), but not in the contralateral denervated kidney (58 ± 3 versus 56 ± 4 ml/min, P > 0.05). 6. These results suggest that intravenously administered l-arginine produces an elevation of renal blood flow, which may be mediated by facilitation of endogenous acetylcholine-induced release of endothelium-derived relaxing factor and vasodilatory prostaglandins.

A DOSE-RESPONSE COMPARISON OF THE ACTIONS OF ANGIOTENSIN II AND ANGIOTENSIN III IN SHEEP

1980 ◽  
Vol 87 (3) ◽  
pp. 409-417 ◽  
Author(s):  
J. R. BLAIR-WEST ◽  
J. P. COGHLAN ◽  
D. A. DENTON ◽  
D. T. W. FEI ◽  
K. J. HARDY ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Angiotensin Ii ◽  
Dose Response ◽  
Plasma Levels ◽  
Secretion Rate ◽  
Cortisol Secretion ◽  
Aldosterone Secretion ◽  
Arterial Blood ◽  
Angiotensin Iii

Comparisons of aldosterone responses to [des-Asp1]-angiotensin II and angiotensin II, often at single dose levels, have shown a wide range of potency ratios. Therefore four-point dose–response comparisons were performed in sodium-replete sheep, using i.v. infusion rates of angiotension II and angiotensin II amide that reproduced the physiological range of blood concentration of angiotensin II for sheep. Angiotensin III was infused i.v. at the same rates. Effects on arterial blood pressure, cortisol secretion rate, adrenal blood flow and plasma levels of Na+ and K+ were also compared. The potency ratio, angiotensin III: angiotensin II amide, was 0·87 for actual aldosterone secretion rate and 0·90 for the calculated increase in aldosterone secretion. For angiotensin III: angiotensin II the ratios were 0·80 and 0·91 respectively. These ratios were not significantly different from 1·00 but the tendency for angiotensin II to be slightly more potent was probably due to a contribution from derived angiotensin III during infusion of angiotensin II. Angiotensin II or angiotensin II amide was ∼ four times as potent as angiotensin III in raising arterial blood pressure. Cortisol secretion rate was slightly but significantly increased by all peptides at the higher infusion rates. Infusions had no effect on adrenal blood flow or plasma levels of Na + but raised plasma levels of K + slightly. These results confirm the conclusion from adrenal arterial infusion experiments that angiotensin II and III are almost equipotent in stimulating aldosterone secretion in sheep.

ADRENAL 17-HYDROXYCORTICOSTEROID SECRETION IN THE DOG IN RESPONSE TO ETHANOL

1972 ◽  
Vol 70 (4) ◽  
pp. 736-740 ◽  
Author(s):  
T. Suzuki ◽  
R. Higashi ◽  
T. Hirose ◽  
H. Ikeda ◽  
K. Tamura
Keyword(s):  
Venous Blood ◽  
Secretion Rate ◽  
Conscious Dogs ◽  
Blood Samples ◽  
Before And After

ABSTRACT Conscious dogs were infused intravenously with ethanol in doses of 0.7 and 1.0 g/kg. The adrenal venous blood samples were collected before and after the infusion of ethanol and analysed for 17-hydroxycorticosteroids (17-OHCS). After the infusion of 0.7 g/kg (subanaesthetic dose) of ethanol the adrenal 17-OHCS secretion rate showed either a slight increase or no change. After the infusion of 1.0 g/kg (anaesthetic dose) of ethanol the adrenal 17-OHCS secretion rate increased markedly and reached 1.21±0.15 (mean±sem) μg/kg/min, while it was 0.09±0.023 μg/kg/min before the infusion.

alpha-Adrenergic control of oxygen delivery to myocardium during exercise in conscious dogs

1982 ◽  
Vol 242 (5) ◽  
pp. H805-H809 ◽  
Author(s):  
G. R. Heyndrickx ◽  
P. Muylaert ◽  
J. L. Pannier
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Oxygen Consumption ◽  
Coronary Blood Flow ◽  
Coronary Sinus ◽  
Oxygen Delivery ◽  
Left Ventricular ◽  
Conscious Dogs ◽  
Adrenergic Blockade ◽  
Adrenergic Control

alpha-Adrenergic control of the oxygen delivery to the myocardium during exercise was investigated in eight conscious dogs instrumented for chronic measurements of coronary blood flow, left ventricular (LV) pressure, aortic blood pressure, and heart rate and sampling of arterial and coronary sinus blood. After alpha-adrenergic receptor blockade a standard exercise load elicited a significantly greater increase in heart rate, rate of change of LV pressure (LV dP/dt), LV dP/dt/P, and coronary blood flow than was elicited in the unblocked state. In contrast to the response pattern during control exercise, there was no significant change in coronary sinus oxygen tension (PO2), myocardial arteriovenous oxygen difference, and myocardial oxygen delivery-to-oxygen consumption ratio. It is concluded that the normal relationship between myocardial oxygen supply and oxygen demand is modified during exercise after alpha-adrenergic blockade, whereby oxygen delivery is better matched to oxygen consumption. These results indicate that the increase in coronary blood flow and oxygen delivery to the myocardium during normal exercise is limited by alpha-adrenergic vasoconstriction.

Adrenocortical response during corrected and uncorrected hypercapnic acidosis

1962 ◽  
Vol 202 (2) ◽  
pp. 334-336 ◽  
Author(s):  
Arnold Mittelman ◽  
Serge J. Dos ◽  
Harold G. Barker ◽  
Gabriel G. Nahas
Keyword(s):  
Flow Rate ◽  
Venous Blood ◽  
Concomitant Administration ◽  
Cortisol Secretion ◽  
Hypercapnic Acidosis ◽  
Sharp Reduction ◽  
Venous Flow ◽  
Arterial Blood ◽  
Blood Ph ◽  
Before And After

Adrenal venous flow rate and cortisol synthesis have been measured in dogs subjected to hypercapnic acidosis before and after intravenous administration of 0.34 mm/kg of tris (hydroxymethyl) amino methane (THAM). A comparison was made of adrenal venous, peripheral venous, and arterial blood, pH, pCO2 and O2 saturation. During uncorrected hypercapnic acidosis the concentration of cortisol increased while adrenal venous flow rate decreased, but there was a significant increase in the minute output of cortisol. With the concomitant administration of 0.34 mM/kg THAM, adrenal venous flow rate doubled. However, since this enhanced flow rate was accompanied by a sharp reduction in cortisol secretion, the minute output of cortisol returned to control levels. The possibility of a direct effect of THAM on the adrenal vascular bed and synthetic processes is discussed. Throughout all the above experiments adrenal venous blood resembled arterial blood rather than peripheral blood in its pCO2, O2 saturation and pH.

Rhythmicity of urinary sodium excretion, mean arterial blood pressure, and heart rate in conscious dogs

1992 ◽  
Vol 262 (1) ◽  
pp. H149-H156 ◽  
Author(s):  
U. Palm ◽  
W. Boemke ◽  
H. W. Reinhardt
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Arterial Blood Pressure ◽  
Mean Arterial Blood Pressure ◽  
Sodium Excretion ◽  
Urinary Sodium Excretion ◽  
Urinary Sodium ◽  
Conscious Dogs ◽  
Arterial Blood ◽  
Infusion Regimen

The existence of urinary excretion rhythms in dogs, which is a matter of controversy, was investigated under strictly controlled intake and environmental conditions. In seven conscious dogs, 14.5 mmol Na, 3.55 mmol K, and 91 ml H2O.kg body wt-1.24 h-1 were either administered with food at 8:30 A.M. or were continuously infused at 2 consecutive days. During these 3 days, automatized 20-min urine collections, mean arterial blood pressure (MABP), and heart rate (HR) recordings were performed without disturbing the dogs. Fundamental and partial periodicities, the noise component of urinary sodium excretion (UNaV), MABP, and HR were analyzed using a method derived from Fourier and Cosinor analysis. Oral intake (OI) leads to powerful 24-h periodicities in all dogs and seems to synchronize UNaV. UNaV on OI peaked between 1 and 3 P.M. Under the infusion regimen, signs of nonstationary rhythms and desynchronization predominated. UNaV under the infusion regimen could be separated into two components: a rather constant component continuously excreted and superimposed to this an oscillating component. No direct coupling between UNaV and MABP periodicities could be demonstrated. On OI, an increase in HR seems to advance the peak UNaV in the postprandial period. HR and MABP signals were both superimposed with noise. We conclude that UNaV rhythms are present in dogs. They are considerably more pronounced on OI.

Enhanced adrenergic constriction of iliac artery with removal of endothelium in conscious dogs

1986 ◽  
Vol 250 (5) ◽  
pp. H892-H897 ◽  
Author(s):  
M. A. Young ◽  
S. F. Vatner
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Iliac Artery ◽  
Conscious Dogs ◽  
Base Line ◽  
Adrenergic Agonists ◽  
Arterial Infusion ◽  
Iliac Arteries ◽  
Acetyl Choline ◽  
Before And After

We studied, in conscious dogs, the effects of removal of endothelium on the responses of iliac artery diameter and iliac blood flow to intra-arterial infusions of adrenergic agonists. With endothelium intact, iliac diameter increased with intra-arterial infusion of nitroglycerin (4.7 +/- 0.4%), acetylcholine (4.2 +/- 0.6%), and epinephrine (4.5 +/- 1.3%), and decreased with norepinephrine (-7.5 +/- 1.7%), phenylephrine (-6.6 +/- 1.0%), and B-HT 920 (-2.1 +/- 0.6%). One- to-five days following removal of endothelium with a balloon-tipped catheter, base-line iliac diameter was unchanged, and still increased with nitroglycerin (4.6 +/- 0.5%), but not with acetyl-choline, and epinephrine actually decreased diameter (-3.5 +/- 1.3%). Removal of the endothelium also enhanced the constriction observed with norepinephrine (-12.5 +/- 2.0%) and phenylephrine (-11.4 +/- 1.6%), but not with B-HT 920 (-1.8 +/- 0.5%). The changes in arterial pressure, iliac blood flow, iliac vascular resistance, and heart rate induced by any of the agonists did not differ before and after removal of the endothelium. These results indicate that the endothelium mediates the dilation in response to epinephrine and also serves an important role in protecting against alpha 1-adrenergic vasoconstriction of large iliac arteries.

scholarly journals The Contribution of Arterial Blood Gases in Cerebral Blood Flow Regulation and Fuel Utilization in Man at High Altitude

2015 ◽  
Vol 35 (5) ◽  
pp. 873-881 ◽  
Author(s):  
Christopher K Willie ◽  
David B MacLeod ◽  
Kurt J Smith ◽  
Nia C Lewis ◽  
Glen E Foster ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
High Altitude ◽  
Cerebral Metabolism ◽  
Venous Blood ◽  
Blood Gases ◽  
Cerebrovascular Reactivity ◽  
Arterial Blood Gases ◽  
Arterial Blood ◽  
Cerebrovascular Function

The effects of partial acclimatization to high altitude (HA; 5,050 m) on cerebral metabolism and cerebrovascular function have not been characterized. We hypothesized (1) increased cerebrovascular reactivity (CVR) at HA; and (2) that CO2 would affect cerebral metabolism more than hypoxia. PaO2 and PaCO2 were manipulated at sea level (SL) to simulate HA exposure, and at HA, SL blood gases were simulated; CVR was assessed at both altitudes. Arterial–jugular venous differences were measured to calculate cerebral metabolic rates and cerebral blood flow (CBF). We observed that (1) partial acclimatization yields a steeper CO2-H+ relation in both arterial and jugular venous blood; yet (2) CVR did not change, despite (3) mean arterial pressure (MAP)-CO2 reactivity being doubled at HA, thus indicating effective cerebral autoregulation. (4) At SL hypoxia increased CBF, and restoration of oxygen at HA reduced CBF, but neither had any effect on cerebral metabolism. Acclimatization resets the cerebrovasculature to chronic hypocapnia.

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