Arterial and arteriolar contributions to skeletal muscle functional hyperemia in spontaneously hypertensive rats

1995 ◽  
Vol 78 (1) ◽  
pp. 93-100 ◽  
Author(s):  
J. M. Lash
Keyword(s):  
Blood Flow ◽  
Spontaneously Hypertensive Rats ◽  
Muscle Blood Flow ◽  
Muscle Contractions ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Wky Rats ◽  
Tissue Po2 ◽  
Wistar Kyoto ◽  
Induced Changes

During contractions of the spinotrapezius muscle in spontaneously hypertensive rats (SHR), arteriolar dilation is of normal magnitude but tissue PO2 is significantly depressed relative to normotensive [Wistar-Kyoto (WKY)] rats. This study examined the possibility that this low PO2 results from suppressed dilation of the upstream arterial feed vessels and a limitation of muscle blood flow. Contraction-induced changes in vascular resistances (R) and conductances (G) were calculated for upstream (Rup, Gup), microvascular (Rst, Gst), and downstream (Rdown, Gdown) vascular segments from measurements of pressure and flow in the rostral feed artery and vein. Feed arteries were smaller in SHR than in WKY rats at rest and after contractions (rest, 63.0 +/- 2.6 vs. 86.0 +/- 4.8 microns; 2 Hz 84.0 +/- 4.5 vs. 111.0 +/- 7.3 microns; 8 Hz, 130.0 +/- 5.9 vs. 144.0 +/- 7.1 microns). However, relative increases [times control (xCT)] in diameter and flow were greater in SHR (8 Hz diam, 2.080 +/- 0.072 vs. 1.690 +/- 0.042 xCT; 8 Hz flow, 15.700 +/- 2.057 vs. 8.170 +/- 0.752 xCT). In both groups, Rup and Rst decreased 60–70 and 85–90% after 2- and 8-Hz contractions, respectively. However, segmental vascular conductances increased more in SHR than in WKY rats (8 Hz: Gup, 18.50 +/- 3.76 vs. 8.00 +/- 1.26 xCT; Gst, 19.90 +/- 3.73 vs. 10.10 +/- 0.96 xCT; Gdown, 8.80 +/- 1.70 vs. 5.50 +/- 0.88 xCT). Therefore, upstream arterial dilation is not suppressed during muscle contractions in SHR, and deficits in muscle blood flow and oxygen delivery cannot account for the abnormally low tissue PO2 observed during muscle contractions in SHR.

Excess oxygen delivery during muscle contractions in spontaneously hypertensive rats

1995 ◽  
Vol 78 (1) ◽  
pp. 101-111 ◽  
Author(s):  
J. M. Lash ◽  
H. G. Bohlen
Keyword(s):  
Blood Flow ◽  
Oxygen Saturation ◽  
Oxygen Delivery ◽  
Spontaneously Hypertensive Rats ◽  
Muscle Contractions ◽  
Hypertensive Rats ◽  
Hemoglobin Oxygen Saturation ◽  
Spontaneously Hypertensive ◽  
Tissue Po2 ◽  
Wistar Kyoto

These experiments determined whether a deficit in oxygen supply relative to demand could account for the sustained decrease in tissue PO2 observed during contractions of the spinotrapezius muscle in spontaneously hypertensive rats (SHR). Relative changes in blood flow were determined from measurements of vessel diameter and red blood cell velocity. Venular hemoglobin oxygen saturation measurements were performed by using in vivo spectrophotometric techniques. The relative dilation [times control (xCT)] of arteriolar vessels during contractions was as large or greater in SHR than in normotensive rats (Wistar-Kyoto), as were the increases in blood flow (2 Hz, 3.50 +/- 0.69 vs. 3.00 +/- 1.05 xCT; 4 Hz, 10.20 +/- 3.06 vs. 9.00 +/- 1.48 xCT; 8 Hz, 16.40 +/- 3.95 vs. 10.70 +/- 2.48 xCT). Venular hemoglobin oxygen saturation was lower in the resting muscle of SHR than of Wistar-Kyoto rats (31.0 +/= 3.0 vs. 43.0 +/- 1.9%) but was higher in SHR after 4- and 8-Hz contractions (4 Hz, 52.0 +/- 4.8 vs. 43.0 +/- 3.6%; 8 Hz, 51.0 +/- 4.6 vs. 41.0 +/- 3.6%). Therefore, an excess in oxygen delivery occurs relative to oxygen use during muscle contractions in SHR. The previous and current results can be reconciled by considering the possibility that oxygen exchange is limited in SHR by a decrease in anatomic or perfused capillary density, arteriovenular shunting of blood, or decreased transit time of red blood cells through exchange vessels.

scholarly journals Exercise changes regional vascular control by commissural NTS in spontaneously hypertensive rats

2010 ◽  
Vol 299 (1) ◽  
pp. R291-R297 ◽  
Author(s):  
Cristiana A. Ogihara ◽  
Gerhardus H. M. Schoorlemmer ◽  
Adriana C. Levada ◽  
Tania C. Pithon-Curi ◽  
Rui Curi ◽  
...  
Keyword(s):  
Arterial Pressure ◽  
Spontaneously Hypertensive Rats ◽  
The Body ◽  
Swimming Exercise ◽  
Exercise Session ◽  
Hypertensive Rats ◽  
Vascular Control ◽  
Spontaneously Hypertensive ◽  
Wky Rats ◽  
Wistar Kyoto

Inhibition of the commissural nucleus of the solitary tract (commNTS) induces a fall in sympathetic nerve activity and blood pressure in spontaneously hypertensive rats (SHR), which suggests that this subnucleus of the NTS is a source of sympathoexcitation. Exercise training reduces sympathetic activity and arterial pressure. The purpose of the present study was to investigate whether the swimming exercise can modify the regional vascular responses evoked by inhibition of the commNTS neurons in SHR and normotensive Wistar-Kyoto (WKY) rats. Exercise consisted of swimming, 1 h/day, 5 days/wk for 6 wks, with a load of 2% of the body weight. The day after the last exercise session, the rats were anesthetized with intravenous α-chloralose, tracheostomized, and artificially ventilated. The femoral artery was cannulated for mean arterial pressure (MAP) and heart rate recordings, and Doppler flow probes were placed around the lower abdominal aorta and superior mesenteric artery. Microinjection of 50 mM GABA into the commNTS caused similar reductions in MAP in swimming and sedentary SHR (−25 ± 6 and −30 ± 5 mmHg, respectively), but hindlimb vascular conductance increased twofold in exercised vs. sedentary SHR (54 ± 8 vs. 24 ± 5%). GABA into the commNTS caused smaller reductions in MAP in swimming and sedentary WKY rats (−20 ± 4 and −16 ± 2 mmHg). Hindlimb conductance increased fourfold in exercised vs. sedentary WKY rats (75 ± 2% vs. 19 ± 3%). Therefore, our data suggest that the swimming exercise induced changes in commNTS neurons, as shown by a greater enhancement of hindlimb vasodilatation in WKY vs. SHR rats in response to GABAergic inhibition of these neurons.

Methionine-enkephalin and vasopressin in SHR: effects of dehydration

1986 ◽  
Vol 250 (6) ◽  
pp. R1007-R1013
Author(s):  
K. Ota ◽  
L. Share ◽  
J. T. Crofton ◽  
D. P. Brooks
Keyword(s):  
Spontaneously Hypertensive Rats ◽  
Posterior Pituitary ◽  
Hypertensive Rats ◽  
Methionine Enkephalin ◽  
Spontaneously Hypertensive ◽  
Wky Rats ◽  
Plasma Vasopressin ◽  
Vasopressin Secretion ◽  
Wistar Kyoto ◽  
Shr And Wky Rats

Enkephalins are found in the posterior pituitary, can alter vasopressin secretion, and have greater pressor effects in spontaneously hypertensive rats (SHR) than in Wistar-Kyoto (WKY) rats. Measurement of the plasma methionine-enkephalin concentration (PMet-Enk) has provided equivocal results in humans and has not been reported in rats. We have developed a highly specific and sensitive Met-Enk radioimmunoassay and determined that Met-Enk circulates in rats but that PMet-Enk is no different between SHR and WKY rats (7.6 +/- 0.8 and 9.2 +/- 0.8 pg/ml, respectively). Water deprivation for 48 h increased the plasma vasopressin concentration (PADH) and 24-h urinary vasopressin excretion (UADHV) in SHR and WKY rats, but PMet-Enk was not altered. There were no differences in PADH and UADHV between SHR and WKY rats in either the euhydrated or dehydrated state. These results suggest that it is unlikely that circulating Met-Enk contributes importantly to the maintenance of hypertension in SHR. There was also no evidence for a greater secretion of vasopressin in SHR than in WKY rats, in contrast to previous reports.

scholarly journals Role of cholinergic receptors in adrenal catecholamine secretion in spontaneously hypertensive rats

1999 ◽  
Vol 277 (4) ◽  
pp. R1057-R1062 ◽  
Author(s):  
Takahiro Nagayama ◽  
Takayuki Matsumoto ◽  
Makoto Yoshida ◽  
Mizue Suzuki-Kusaba ◽  
Hiroaki Hisa ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Muscarinic Receptors ◽  
Nicotinic Receptors ◽  
Spontaneously Hypertensive Rats ◽  
Adrenal Glands ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Wky Rats ◽  
Wistar Kyoto

We investigated the role of nicotinic and muscarinic receptors in secretion of catecholamines induced by transmural electrical stimulation (ES) from isolated perfused adrenal glands of spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats. ES (1–10 Hz) produced frequency-dependent increases in epinephrine (Epi) and norepinephrine (NE) output as measured in perfusate. The ES-induced increases in NE output, but not Epi output, were significantly greater in adrenal glands of SHRs than in those of WKY rats. Hexamethonium (10–100 μM) markedly inhibited the ES-induced increases in Epi and NE output from adrenal glands of SHRs and WKY rats. Atropine (0.3–3 μM) inhibited the ES-induced increases in Epi and NE output from adrenal glands of SHRs, but not from those of WKY rats. These results suggest that endogenous acetylcholine-induced secretion of adrenal catecholamines is predominantly mediated by nicotinic receptors in SHRs and WKY rats and that the contribution of muscarinic receptors may be different between these two strains.

scholarly journals Effect of a methionine-supplemented diet on the blood pressure of Wistar–Kyoto and spontaneously hypertensive rats

2003 ◽  
Vol 89 (4) ◽  
pp. 539-548 ◽  
Author(s):  
Sophie Robin ◽  
Véronique Maupoil ◽  
Frédérique Groubatch ◽  
Pascal Laurant ◽  
Alain Jacqueson ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Spontaneously Hypertensive Rats ◽  
Plasma Homocysteine ◽  
Shr Rats ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Wky Rats ◽  
Complex Interactions ◽  
Methionine Concentration ◽  
Wistar Kyoto

The objectives of the present work were to evaluate the effect of a methionine-supplemented diet as a model of hyperhomocysteinaemia on the systolic blood pressure (BP) and vasomotor functions of aortic rings in Wistar–Kyoto (WKY) and spontaneously hypertensive rats (SHR). WKY and SHR rats, randomised into four groups, were fed a normal semisynthetic diet or a methionine (8 g/kg)-supplemented diet for 10 weeks. Systolic BP was measured non-invasively. At the end of the experiment, plasma homocysteine, methionine, cysteine and glutathione levels were determined. Vasoconstriction and vasodilatation of aortic rings were measured. The methionine-supplemented diet induced a significant increase in plasma homocysteine and methionine concentration in both WKY and SHR rats, an increase in plasma cysteine concentrations in WKY rats and an increase in the glutathione concentration in SHR. The systolic BP of WKY rats fed the methionine-supplemented diet increased significantly (P<0·01), whereas systolic BP was reduced in SHR. An enhanced aortic responsiveness to noradrenaline and a decreased relaxation induced by acetylcholine and bradykinin were observed in the WKY rats fed the methionine-enriched diet. In SHR, the bradykinin-induced relaxation was reduced, but the sodium nitroprusside response was increased. In conclusion, a methionine-enriched diet induced a moderate hyperhomocysteinaemia and an elevated systolic BP in WKY rats that was consistent with the observed endothelial dysfunction. In SHR, discrepancies between the decreased systolic BP and the vascular alterations suggest more complex interactions of the methionine-enriched diet on the systolic BP. Further investigations are needed to understand the paradoxical effect of a methionine-rich diet on systolic BP.

Clonidine fails to reduce pressor responsiveness of conscious spontaneously hypertensive rats to vasopressin

1986 ◽  
Vol 64 (3) ◽  
pp. 284-289 ◽  
Author(s):  
Sunil Datar ◽  
William H. Laverty ◽  
J. Robert McNeill
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
Spontaneously Hypertensive Rats ◽  
Reflex Activity ◽  
Unexpected Finding ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Wky Rats ◽  
Wistar Kyoto ◽  
Shr And Wky Rats

Pressor responses and heart rate responses to intravenous injections (3.5–50.0 pmol/kg) of arginine vasopressin (AVP) were recorded in saline- and clonidine-treated spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. Clonidine (20 μg/kg, i. v.) caused a marked fall of arterial pressure in SHR but not in WKY rats so that, 20 min after the injection of the α2-adrenoceptor agonist, arterial pressure was similar in the two strains of rats. The curve expressing the relationship between the dose of AVP and the increase of arterial pressure for saline-treated SHR was positioned to the left of that for saline-treated WKY rats. This enhanced pressor responsiveness of SHR to AVP may have been related to impaired reflex activity since heart rate fell much less in SHR than in WKY rats for a given elevation in pressure. Pressure responses to AVP were augmented by clonidine in both SHR and WKY rats so that, similar to saline-treated rats, pressor responsiveness to the peptide was still greater in SHR. Heart rate responses to AVP were not altered significantly by clonidine. The results indicate that clonidine fails to enhance reflex activity and reduce pressor responsiveness of SHR to AVP. The increased pressor responsiveness of both SHR and WKY rats to AVP following clonidine was an unexpected finding and may be related to a peripheral interaction between α-adrenergic agonists and AVP.

scholarly journals Physiological and Behavioral Effects of d-threo-methylphenidate Hydrochloride in Male Wistar-Kyoto and Spontaneously Hypertensive Rats

2003 ◽  
Vol 2 (2) ◽  
Author(s):  
Jennifer Sayler ◽  
Linda Tennison ◽  
David Mitchell
Keyword(s):  
Working Memory ◽  
Spontaneously Hypertensive Rats ◽  
Spatial Working Memory ◽  
Membrane Lipids ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Glucose Levels ◽  
Wky Rats ◽  
Physiological Properties ◽  
Wistar Kyoto

Millions of children and adults worldwide are diagnosed with Attention-deficit hyperactivity disorder (ADHD) and yet its very existence, definition, and treatment are surrounded with discord and controversy. ADHD and its treatments are brought together through this investigation into the effects that drug therapy has on Wistar Kyoto rats (WKY) and a strain of Spontaneously Hypertensive rats (SHR) selectively inbred from WKY rats. The effects of the drug d-threo-methylphenidate hydrochloride (d-MPH - the d-isomer of the ADHD drug Ritalin) on spatial working memory abilities, overall growth rate, blood glucose levels, blood pH, and erythrocyte membrane lipids were examined in the two rat strains. Although all four physiological properties remained constant and normal over the course of the experiment, the spatial working memory abilities were inhibited in WKY rats receiving the drug. These results suggest that the d-isomer of this drug may have a significant impact on cognitive function in rats and possibly humans.

Cerebral artery responses to pressure and flow in uremic hypertensive and spontaneously hypertensive rats

2003 ◽  
Vol 284 (4) ◽  
pp. H1212-H1216 ◽  
Author(s):  
D. I. New ◽  
A. M. S. Chesser ◽  
R. C. Thuraisingham ◽  
M. M. Yaqoob
Keyword(s):  
Blood Flow ◽  
Cerebral Artery ◽  
Spontaneously Hypertensive Rats ◽  
Perfusion Pressure ◽  
Hypertensive Rats ◽  
Independent Manner ◽  
Spontaneously Hypertensive ◽  
Cerebral Blood Flow Autoregulation ◽  
Wistar Kyoto ◽  
Normotensive Control

Impaired cerebral blood flow autoregulation is seen in uremic hypertension, whereas in nonuremic hypertension autoregulation is shifted toward higher perfusion pressure. The cerebral artery constricts in response to a rise in either lumen pressure or flow; we examined these responses in isolated middle cerebral artery segments from uremic Wistar-Kyoto rats (WKYU), normotensive control rats (WKYC), and spontaneously hypertensive rats (SHR). Pressure-induced (myogenic) constriction developed at 100 mmHg; lumen flow was then increased in steps from 0 to 98 μl/min. Some vessels were studied after endothelium ablation. Myogenic constriction was significantly lower in WKYU (28 ± 2.9%) compared with both WKYC (39 ± 2.5%, P = 0.035) and SHR (40 ± 3.1%, P = 0.018). Flow caused constriction of arteries from all groups in an endothelium-independent manner. The response to flow was similar in WKYU and WKYC, whereas SHR displayed increased constriction compared with WKYU ( P < 0.001) and WKYC ( P < 0.001). We conclude that cerebral myogenic constriction is decreased in WKYU, whereas flow-induced constriction is enhanced in SHR.

Resetting of renal blood flow autoregulation in spontaneously hypertensive rats

1987 ◽  
Vol 252 (3) ◽  
pp. F480-F486 ◽  
Author(s):  
B. M. Iversen ◽  
I. Sekse ◽  
J. Ofstad
Keyword(s):  
Blood Flow ◽  
Renal Blood Flow ◽  
Spontaneously Hypertensive Rats ◽  
Lower Pressure ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Pressure Limit ◽  
Wistar Kyoto ◽  
Renal Vascular ◽  
Renal Blood Flow Autoregulation

Renal blood flow (RBF) autoregulation was examined in untreated 10- and 40-wk-old spontaneously hypertensive rats (SHR) [mean arterial pressure (MAP) 125 +/- 4 and 167 +/- 7 mmHg] and in captopril-treated (7 days) 10- and 40-wk-old SHR (88 +/- 7 and 112 +/- 5 mmHg). Age-matched Wistar-Kyoto rats (WKY) were used as controls (MAP 91 +/- 3 and 104 +/- 2 mmHg). The study was carried out in rats with and without acute uninephrectomy. In 10-wk-old acutely uninephrectomized animals, the lower pressure limit of autoregulation was 78 +/- 4 mmHg in WKY, 102 +/- 5 mmHg in SHR (P less than 0.02), and 78 +/- 7 mmHg in captopril-treated SHR (P greater than 0.10). The renal vascular resistance (RVR) was significantly elevated at the lower pressure limit of RBF autoregulation in untreated SHR (P less than 0.02) but became normal after treatment (P greater than 0.10). Neither uninephrectomy nor variation of RBF between different batches seemed to influence the lower pressure limit of RBF autoregulation. In 40-wk-old acutely nephrectomized animals, the lower pressure limit of RBF autoregulation in WKY was 85 +/- 4 mmHg, 128 +/- 3 mmHg in SHR (P less than 0.001), and 101 +/- 5 mmHg in captopril-treated SHR (P less than 0.01). RVR at the lower pressure limit was increased in untreated SHR (P less than 0.01), but fell to normal values during captopril treatment. Neither the uninephrectomy nor variation of RBF between different batches of rats seemed to influence the lower pressure limit of RBF autoregulation.(ABSTRACT TRUNCATED AT 250 WORDS)

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