Microvascular responses to norepinephrine in renovascular and spontaneously hypertensive rats

1979 ◽  
Vol 236 (4) ◽  
pp. H545-H548 ◽  
Author(s):  
D. L. Wiegman ◽  
I. G. Joshua ◽  
R. J. Morff ◽  
P. D. Harris ◽  
F. N. Miller
Keyword(s):  
Spontaneously Hypertensive Rats ◽  
Cremaster Muscle ◽  
Sprague Dawley ◽  
Hypertensive Rats ◽  
Small Artery ◽  
Response Curves ◽  
Spontaneously Hypertensive ◽  
Small Vein ◽  
Wistar Kyoto

Closed-circuit television microscopy was used to quantitate the responses of in vivo small arteries (50-140 micrometer diam) and veins (95-265 micrometer) to topically applied norepinephrine in the cremaster muscle of four groups of urethan-chloralose anesthetized rats. The rat groups were: Sprague-Dawley control (SDC), Sprague-Dawley renovascular hypertensive (RVH), Wistar-Kyoto control (WKY), and spontaneous hypertensive (SHR). The cremaster muscle with intact circulation and innervation was suspended by sutures in a 60-ml bath of bicarbonate-buffered Krebs solution. The vascular responses to the addition of progressively higher concentrations of norepinephrine to the bath were quantitated to obtain concentration-response curves. We found that the RVH (vs. SDC) had a decreased small-artery control diameter and decreased sensitivity to norepinephrine, whereas the SHR (vs. WKY) had tachycardia and decreased small-vein control diameter. Thus, the microvascular characteristics of these two types of hypertension appear to be quite different.

Altered muscle metabolism associated with vasoconstriction in spontaneously hypertensive rats

1998 ◽  
Vol 275 (6) ◽  
pp. E1007-E1015 ◽  
Author(s):  
Ji-Ming Ye ◽  
Eric Q. Colquhoun
Keyword(s):  
Glucose Uptake ◽  
Spontaneously Hypertensive Rats ◽  
Perfusion Pressure ◽  
Lactate Production ◽  
Ang Ii ◽  
Hypertensive Rats ◽  
Response Curves ◽  
Spontaneously Hypertensive ◽  
Wistar Kyoto

In the rat muscle vascular bed, vasoconstrictors either increase or decrease oxygen consumption (V˙o 2). The present study compared the effects of norepinephrine (NE), angiotensin II (ANG II), and 5-hydroxytryptamine (5-HT) on vasoconstriction-associated metabolism in the constant-flow perfused hindlimb of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) in the absence of insulin. Basal perfusion pressure,V˙o 2, glucose uptake, and lactate production were increased by 21.4, 11.9, 46.4, and 44.9% ( P < 0.05 for all), respectively, in SHR, which also had higher blood pressure and metabolic rate ( P < 0.05) in vivo. Dose-response curves for NE-induced perfusion pressure,V˙o 2, and lactate production in SHR were shifted to the left compared with WKY. Associated with the increased perfusion pressure, NE-inducedV˙o 2 and glucose uptake were both decreased ( P < 0.01), particularly at high concentrations. These differences were unaffected by 10 μM propranolol but were all diminished by further addition of prazosin (2.5 nM). ANG II stimulatedV˙o 2, glucose uptake, and lactate production in both strains, but the increased lactate production was smaller in SHR ( P < 0.05) with a proportional decrease ( P< 0.05) in glucose uptake. Conversely, 5-HT decreasedV˙o 2 in both strains ( P < 0.01), and this effect was greater in SHR ( P < 0.01). These data suggest that SHR muscle thermogenesis and glucose uptake are impaired during vasoconstriction, especially in response to NE.

Decreased in vitro responses to vasoconstrictors during gestation in normotensive and spontaneously hypertensive rats

1987 ◽  
Vol 65 (12) ◽  
pp. 2466-2471 ◽  
Author(s):  
G. Massicotte ◽  
J. St-Louis ◽  
A. Parent ◽  
E. L. Schiffrin
Keyword(s):  
Spontaneously Hypertensive Rats ◽  
Female Rats ◽  
Sprague Dawley ◽  
Hypertensive Rats ◽  
Response Curves ◽  
Pregnant Rats ◽  
Spontaneously Hypertensive ◽  
Vasoconstrictor Agents ◽  
Wistar Kyoto

We have investigated the in vitro vascular responses to vasoconstrictor agents in pregnant normotensive (Sprague–Dawley (SDR) and Wistar–Kyoto (WKR)) and spontaneously hypertensive rats (SHR) to measure the sensitivity and contractility of blood vessels of pregnant rats. In the perfused mesenteric vascular bed from rats on the 21st day of gestation, the concentration–response curves for the increase in perfusion pressure by arginine8-vasopressin and norepinephrine were displaced to the right by comparison to nonpregnant female rats when all strains of rats were considered together. The increase in EC50 to both agents in pregnant rats was from 1.3- to 2.7-fold in the mesenteric bed; SDR showed the highest increase in EC50, followed by SHR and WKR. No consistent effect was observed on the maximum response. Similar results were obtained in isolated portal veins for angiotensin II and norepinephrine, except that the increase in EC50 in pregnant rats was smaller in magnitude (from 1.0 to 1.7) and followed the same interstrain pattern. These data show that the decreased responsiveness to vasoconstrictor agents in pregnant rats observed in vitro is similar in normotensive and hypertensive rats and suggest that the factor(s) responsible for this effect is a phenomenon affecting vascular smooth muscle in both arteries and veins.

Effect of destruction of the vascular endothelium upon pressure/flow relations and endothelium-dependent vasodilatation in resistance beds of spontaneously hypertensive rats

1991 ◽  
Vol 80 (5) ◽  
pp. 463-469 ◽  
Author(s):  
Michael D. Randall ◽  
G. Roger Thomas ◽  
C. Robin Hiley
Keyword(s):  
Spontaneously Hypertensive Rats ◽  
Regression Line ◽  
Hypertensive Rats ◽  
Response Curves ◽  
Pressure Flow ◽  
Spontaneously Hypertensive ◽  
Wistar Kyoto Rats ◽  
Vascular Beds ◽  
Wistar Kyoto

1. Pressure/flow relationships were determined in the in situ blood-perfused superior mesenteric and hindquarters vascular beds of spontaneously hypertensive rats and Wistar-Kyoto normotensive rats before and after destruction of the endothelium with detergent. The effects of indomethacin on the regression of pressure on flow were also investigated in the spontaneously hypertensive rats, as were the endothelium-dependent relaxations in response to carbachol in the mesenteric bed. 2. In the spontaneously hypertensive rats the regression line of pressure on flow in the two vascular beds was both steeper and more elevated than in the Wistar-Kyoto rats, showing that there was greater resistance to flow in the hypertensive animals. Destruction of the endothelium significantly increased the slope of the regression in both Wistar-Kyoto and spontaneously hypertensive rats: the increases in the Wistar-Kyoto rats were 2.4 ± 0.3 fold (mesenteric) and 2.0 ± 0.5 fold (hindquarters) which were comparable with the respective increases of 1.6 ± 0.3 fold and 1.8 ± 0.3 fold in the spontaneously hypertensive rats. 3. Indomethacin (5 mg/kg, intravenously) had no effect on the pressure/flow relations in either of the vascular beds of the spontaneously hypertensive rats. 4. The dose-response curves for the endothelium-dependent vasodilatation in response to carbachol were not significantly different in spontaneously hypertensive and Wistar-Kyoto rats. 5. The results suggest that tonic release of endothelium-derived relaxing factor has similar effects in modulating resistance vessel tone in vivo in both hypertensive and normotensive rats. Further, endothelium-dependent vasodilatation does not appear to be impaired in the mesenteric vasculature in spontaneously hypertensive rats, and there appears to be no significant modulation of mesenteric vascular resistance by tonic release of cyclo-oxygenase products in spontaneously hypertensive rats.

scholarly journals Effects of dietary salt on angiotensin peptides in kidney.

1995 ◽  
Vol 6 (4) ◽  
pp. 1209-1215
Author(s):  
Q C Meng ◽  
J Durand ◽  
Y F Chen ◽  
S Oparil
Keyword(s):  
Angiotensin Ii ◽  
Spontaneously Hypertensive Rats ◽  
Spontaneously Hypertensive Rat ◽  
Sprague Dawley ◽  
Dietary Salt ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Angiotensin Peptides ◽  
Sprague Dawley Rats ◽  
Wistar Kyoto

This study used a novel simple method for the extraction, separation, identification, and quantitation of angiotensin-like immunoactivity from tissue to examine the effects of altering dietary NaCl intake on intrarenal angiotensin I, II, and III levels in salt-sensitive, spontaneously hypertensive rats, salt-resistant Wistar-Kyoto rats, and Sprague-Dawley rats. Seven-week-old male spontaneously hypertensive rats, Wistar-Kyoto rats, and Sprague-Dawley rats were assigned randomly to a diet containing either 8% (high) or 1% (basal) salt and were maintained on these diets for 3 wk. Rats were then decapitated without prior anesthesia, and kidneys were rapidly (< 30 s) removed, snap frozen in liquid nitrogen, and stored at -80 degrees C. Frozen tissue was extracted in 2 M acetic acid and then subjected to solid-phase extraction with the cation exchange resin AG 50W X4. Angiotensin peptides were separated by reversed-phase high-performance liquid chromatography on a phenyl silica gel column with an eluent consisting of 20% acetonitrile in 0.1 M ammonium phosphate buffer, pH 4.9, and quantitated by radioimmunoassay. The elution of standard peptides under isocratic conditions revealed clear resolution of angiotensin I, II, and III and the (1-7) and (3-8) peptides. Recoveries of both labeled and unlabeled angiotensin peptide standards from the extraction step were > 90%. Renal angiotensin II stores were significantly higher in spontaneously hypertensive rats than in Wistar-Kyoto or Sprague-Dawley rats, independent of diet. Renal angiotensin II and III were further suppressed during dietary salt supplementation in both salt-resistant strains but not in the spontaneously hypertensive rat. These findings are consistent with an enhanced (compared with Wistar-Kyoto and Sprague-Dawley rats) role for angiotensin II in the kidney of the salt-sensitive, spontaneously hypertensive rat, particularly under conditions of dietary salt supplementation.

The vascular sensitizing character of plasma from spontaneously hypertensive rats

1981 ◽  
Vol 59 (11) ◽  
pp. 1111-1116 ◽  
Author(s):  
Gary L. Wright
Keyword(s):  
Blood Pressure ◽  
Plasma Levels ◽  
Spontaneously Hypertensive Rats ◽  
Vascular Tissue ◽  
Sprague Dawley ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Tissue Sensitivity ◽  
Low Levels ◽  
Wistar Kyoto

Experiments were conducted to examine the effects of plasma from spontaneously hypertensive rats (systolic blood pressure (SBP) = 183 torr; 1 torr = 133.322 Pa) on the contractile properties of aortic strips from normotensive rats. While incubated in plasma from spontaneously hypertensive (SH) rats, the aortic strips of normotensive rats exhibited hyperresponsiveness to norepinephrine (NE) compared with those incubated in plasma obtained from Wistar–Kyoto (SBP = 128 torr) or Sprague–Dawley (SBP = 110 torr) rats. The washout of plasma and perfusion of the aortic strips with Krebs bicarbonate solution abolished the effect of SH plasma on the reactivity to NE but not potassium, suggesting a residual hypersensitivity. The comparison of these findings with results obtained for contractions of aortic strips in Krebs bicarbonate solution containing high and low levels of calcium indicated the effect of SH plasma on vascular tissue sensitivity was not directly related to an alteration in plasma levels of calcium.

Cytoplasmic free [Ca2+] is not increased in the platelets of deoxycorticosterone–salt and spontaneously hypertensive rats

1986 ◽  
Vol 71 (1) ◽  
pp. 121-123 ◽  
Author(s):  
Koh-Ichi Murakawa ◽  
Yoshiharu Kanayama ◽  
Masakazu Kohno ◽  
Takahiko Kawarabayashi ◽  
Kenichi Yasunari ◽  
...  
Keyword(s):  
Spontaneously Hypertensive Rats ◽  
Free Calcium ◽  
Sprague Dawley ◽  
Hypertensive Rats ◽  
Acetoxymethyl Ester ◽  
Spontaneously Hypertensive ◽  
Sprague Dawley Rats ◽  
Significant Difference ◽  
Free Calcium Concentration ◽  
Wistar Kyoto

1. The cytoplasmic free calcium concentration ([Ca2+]i) in the platelets of spontaneously hypertensive rats (SHR), Wistar–Kyoto rats (WKY), deoxycorticosterone–salt hypertensive rats (DOC) and normotensive Sprague–Dawley rats (SD) was measured with the fluorescent dye, quin-2-tetra-acetoxymethyl ester. 2. No significant difference in platelet [Ca2+]i was found between SHR and WKY or between DOC and SD rats. 3. No correlations were found between systolic blood pressure and [Ca2+]i. 4. These results suggest that the elevation of platelet [Ca2+]i does not necessarily accompany hypertension in rats.

Role of vagal afferents in vasodepressor effects of PGE2 in spontaneously hypertensive rats

1979 ◽  
Vol 236 (4) ◽  
pp. H635-H639
Author(s):  
D. S. Chen ◽  
D. E. Donald ◽  
J. C. Romero
Keyword(s):  
Spontaneously Hypertensive Rats ◽  
Jugular Vein ◽  
Vagal Afferents ◽  
Sprague Dawley ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Cervical Vagotomy ◽  
Wistar Kyoto ◽  
Cardiopulmonary Receptors ◽  
Depressor Effect

In anesthetized, spontaneously hypertensive rats (Okamoto-Aoki), injections of 0.75, 1.5, and 3.0 microgram/kg PGE2 into the jugular vein caused transient decreases (mean +/- SE) in arterial pressure of 21 +/- 2, 37 +/- 3, and 78 +/- 6 mmHg, respectively, before cervical vagotomy and of 1 +/- 1, 15 +/- 4, and 15 +/- 6 mmHg after cervical vagotomy. The vasodepressor effect of jugular vein injections of 3.0 microgram/kg PGE2, but not of lower doses, was depressed by vagotomy in normotensive Wistar-Kyoto and Sprague-Dawley rats. Vagotomy did not reduce the hypotensive response to intra-aortic injections of PGE2 in these hypertensive and normotensive rats. The depressor effect of PGE2 thus appears to have a significant reflex component mediated through cardiopulmonary receptors subserved by vagal afferents, with hypertensive rats exhibiting a lower threshold than normotensive rats. A vagally mediated reflex component to the depressor effect of PGE2 could not be demonstrated in normotensive rabbits or in rabbits and rats with chronic renovascular hypertension. Thus, a naturally occurring vasoactive substance can stimulate cardiopulmonary receptors subserved by vagal afferents in the rat, and spontaneously hypertensive rats appear to be especially sensitive to this effect.

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