Calcium reactivity and antagonism in portal veins from spontaneously hypertensive and normotensive rats

1984 ◽  
Vol 62 (1) ◽  
pp. 146-150 ◽  
Author(s):  
A. L. Harris ◽  
V. C. Swamy ◽  
D. J. Triggle
Keyword(s):  
Inhibitory Activity ◽  
Spontaneously Hypertensive Rats ◽  
Age Groups ◽  
Induced Responses ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Activity Frequency ◽  
Blood Pressures ◽  
Portal Veins ◽  
Wistar Kyoto

Reactivities of portal veins from spontaneously hypertensive rats (SHR) and normotensive controls (Wistar Kyoto, WKY) at 5–7 and 15–17 weeks of age were compared. Systolic blood pressures were not different at 5–7 weeks but those of SHR were significantly elevated (177 ± 4 mmHg) (1 mmHg = 133.322 Pa) at 15–17 weeks. Spontaneous activity, frequency, and tension were greater in SHR for both age groups. Young SHR were more sensitive to K+ at 5–7 weeks but less sensitive at 15–17 weeks than age-matched WKY rats. Sensitivity to Ca2+ in a K+-depolarizing medium was higher in SHR than in WKY for both age groups. Maximum tension responses to K+ or Ca2+ were greater in SHR. The Ca2+ channel antagonists nifedipine, nitrendipine, and nisoldipine were potent inhibitors of both noradrenaline- and K+-induced responses but did not show differences in inhibitory activity between WKY and SHR.

Organ specificity of the dopamine1 receptor/adenylyl cyclase coupling defect in spontaneously hypertensive rats

1993 ◽  
Vol 264 (4) ◽  
pp. R726-R732 ◽  
Author(s):  
R. A. Felder ◽  
S. Kinoshita ◽  
K. Ohbu ◽  
M. M. Mouradian ◽  
D. R. Sibley ◽  
...  
Keyword(s):  
Adenylyl Cyclase ◽  
Spontaneously Hypertensive Rats ◽  
Radioligand Binding ◽  
Receptor Gene ◽  
Age Groups ◽  
Organ Specificity ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Wistar Kyoto ◽  
Renal Dopamine

The coupling between the dopamine1 (DA1) receptor and the G protein/adenylyl cyclase (AC) enzyme complex is defective in the proximal convoluted tubule (PCT) of 20-wk-old spontaneously hypertensive rats (SHRs). Because this coupling defect could have been due to desensitization secondary to elevated renal dopamine levels in the adult animal, we studied the interaction between DA1 receptors and AC in PCT of rats as early as 3 wk of age, a time when renal dopamine levels are similar in SHRs and their normotensive controls (Wistar-Kyoto rats, WKYs). Maximum receptor density did not change with age and was similar in WKYs and SHRs in all the age groups studied (3, 8, and 20 wk). Basal-, forskolin-, and guanyl nucleotide-stimulated AC activities were also similar in WKYs and SHRs and did not change with age. However, the DA1 agonist-stimulated AC activity was greater in WKYs than in SHRs and increased with age in WKYs but not in SHRs. Moreover, the ability of a nonhydrolyzable analogue of GTP, Gpp(NH)p, to enhance DA1 agonist (SND-919-C12, 1 microM)-stimulated AC activity increased with age in WKY but not in SHRs. To determine if the defect noted in the PCT of SHRs is due to a defective D1A receptor gene, parallel studies were performed in the striatum, since this receptor is expressed predominantly in the latter tissue. In contrast to the results in PCT, radioligand binding and AC studies in striatum revealed no differences between WKYs and SHRs.(ABSTRACT TRUNCATED AT 250 WORDS)

Vasopressin in brain of spontaneously hypertensive rats

1982 ◽  
Vol 242 (4) ◽  
pp. H496-H499 ◽  
Author(s):  
W. Rascher ◽  
R. E. Lang ◽  
T. Unger ◽  
D. Ganten ◽  
F. Gross
Keyword(s):  
Blood Pressure ◽  
Plasma Concentration ◽  
Brain Stem ◽  
Spontaneously Hypertensive Rats ◽  
Age Groups ◽  
Plasma Osmolality ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Wistar Kyoto ◽  
The Brain

In stroke-prone spontaneously hypertensive rats (SHRSP) and in normotensive Wistar-Kyoto rats (WKY), arginine vasopressin (AVP) was measured by means of a radioimmunoassay in the plasma, the pituitary gland, the hypothalamus, and the brain stem. In 6- and 14-wk-old SHRSP, the plasma concentration of AVP was lower than in age-matched WKY (P less than 0.01), whereas it was elevated at 28 wk of age (P less than 0.01). In the pituitary of 6-wk-old SHRSP, AVP was higher than in WKY (P less than 0.05), but no such difference was found in older rats. In the hypothalamus and the brain stem, AVP content was reduced in all age groups of SHRSP. Plasma osmolality was diminished in 28-wk-old SHRSP only (P less than 0.01), whereas hematocrit in all age groups was higher in SHRSP than in WKY. It is concluded that the secretion of AVP and possibly its synthesis in the hypothalamus are reduced in SHRSP. Whether the reduced AVP content in the brain stem is related to the sustained elevation of blood pressure has to be studied further.

Cell Membrane Microviscosity and Ca2+-Mg2+-ATPase Activity do Not Contribute to Hypertension in the Spontaneously Hypertensive Rat Model

1993 ◽  
Vol 85 (5) ◽  
pp. 585-591 ◽  
Author(s):  
Robert I Norman ◽  
Navtej Achall
Keyword(s):  
Blood Pressure ◽  
Atpase Activity ◽  
Spontaneously Hypertensive Rats ◽  
Spontaneously Hypertensive Rat ◽  
Hypertensive Rats ◽  
Membrane Microviscosity ◽  
Spontaneously Hypertensive ◽  
Blood Pressures ◽  
Wistar Kyoto ◽  
Spontaneously Hypertensive Rat Model

1. The relationships between systolic blood pressure and altered erythrocyte Ca2+-Mg2+-ATPase activity and membrane microviscosity were assessed in membranes prepared from 20-week-old female Wistar-Kyoto normotensive and spontaneously hypertensive rats obtained from two different sources (Charles River and Harlan OLAC) and a second filial (F2) generation derived from a cross between Wistar-Kyoto rats and spontaneously hypertensive rats from one source (Charles River). 2. Spontaneously hypertensive rats from both sources had systolic blood pressures significantly higher than those of Wistar-Kyoto animals (P <0.05; 151 + 4 and 110 + 3 mmHg, Charles River; 155 + 4 and 122 + 4 mmHg, Harlan OLAC). The systolic blood pressures for the F2 rat population ranged between 73 and 168 mmHg. 3. Ca2+-Mg2+-ATPase activity was measured as ATP-dependent 45Ca2+ uptake into inside-out vesicles and microviscosity assessed by the measurement of polarization anisotropy of membrane incorporated fluorescent probes including 1,6-diphenyl-1,3,5-hexatriene, trimethylamino-1,6-diphenyl-1,3,5-hexatriene and a series of anthroyloxy fatty acids. 4. Contrary to previous studies, no relationship between adult systolic blood pressure and erythrocyte Ca2+-Mg2+-ATPase activity or general or localized membrane microviscosity was indicated by the comparison of spontaneously hypertensive and Wistar-Kyoto animals or in the analysis of the F2 rat population. 5. These results suggest that Ca2+-Mg2+-ATPase activity and membrane microviscosity are causally unrelated to hypertension in these animals. On the assumption that biophysical properties of the erythrocyte membrane reflect those of smooth muscle, our results suggest that membrane alteration does not play a significant role in the pathogenesis of hypertension in the spontaneously hypertensive rat model.

Plasma parathyroid hormone during the development of spontaneous hypertension in rats

1987 ◽  
Vol 65 (12) ◽  
pp. 2386-2389 ◽  
Author(s):  
P. K. T. Pang ◽  
S. Harvey ◽  
P. A. Doris
Keyword(s):  
Parathyroid Hormone ◽  
Spontaneously Hypertensive Rats ◽  
Spontaneous Hypertension ◽  
Hypertensive Rats ◽  
Intact Pth ◽  
Spontaneously Hypertensive ◽  
Blood Pressures ◽  
Wistar Kyoto ◽  
Tail Cuff

Plasma parathyroid hormone levels (pPTH) have been measured by radioimmunoassay (RIA) in young spontaneously hypertensive rats (SHR) and normotensive Wistar–Kyoto controls (WKY) aged from 6 to 16 weeks to assess the possible role of PTH during the development of hypertension. Three antisera were used in the RIAs. One antiserum was directed toward the inactive C-terminal fragment of PTH, another toward the bioactive N-terrninal fragment (PTH 1–34), and a third was obtained by immunization against intact PTH 1–84. Blood pressures were measured by tail-cuff plethysmography with prewarming. Blood ionized calcium and sodium concentrations (b[Ca2+] and b[Na+]) were determined by ion-selective electrolyte analysis. No significant differences were observed between pPTH in the SHR compared with WKY during the development of hypertension. Neither were significant differences in b[Ca2+] or b[Na+] present at any age. The expected progression of hypertension in SHRs was observed and blood pressure was significantly greater in SHR than in WKY at all times. The results suggest that differences in pPTH and b[Ca2+] in SHR reported in other studies may be secondary phenomena to the establishment of hypertension. Our data suggest that PTH is not involved in the pathogenetic processes occurring during the development of spontaneous hypertension in rats.

The responses of carotid vascular strips from spontaneously hypertensive and normotensive rats

1980 ◽  
Vol 58 (1) ◽  
pp. 53-59 ◽  
Author(s):  
V. C. Swamy ◽  
D. J. Triggle
Keyword(s):  
Smooth Muscle ◽  
Spontaneously Hypertensive Rats ◽  
Carotid Arteries ◽  
Age Groups ◽  
Extracellular Calcium ◽  
Induced Responses ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Vascular Responses ◽  
Carotid Arterial

The responses to noradrenaline (NA) and KCl of carotid arterial strips from spontaneously hypertensive rats (SHR) and three strains of normotensive rats (NR) were compared using tissues obtained from young (5–7 weeks) or older (15–17 weeks) rats. The maximum responses and sensitivity of strips from SHR were less than those of NR in both age groups. Relaxation of maximum NA-induced responses was consistently faster, and relaxation of KCl-induced responses generally slower with strips from SHR. Carotid strips from young SHR showed a greater dependence on extracellular calcium in their responses to NA and a lesser dependence in their KCl-induced responses than tissues from NR. We conclude that the smooth muscle of carotid arteries from SHR differs intrinsically from that of NR and that the differences in vascular responses may be related to altered excitation-contraction processes in the SHR.

Inhibition by cinnarizine of the responses of smooth muscle from spontaneously hypertensive and normotensive rats

1983 ◽  
Vol 61 (12) ◽  
pp. 1523-1525 ◽  
Author(s):  
C. Nghiem ◽  
V. C. Swamy ◽  
D. J. Triggle
Keyword(s):  
Smooth Muscle ◽  
Calcium Antagonist ◽  
Spontaneously Hypertensive Rats ◽  
Carotid Arteries ◽  
Induced Responses ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Tissue Responses ◽  
Wistar Kyoto ◽  
Carotid Arterial

A comparison was made of the inhibition by cinnarizine, a calcium antagonist, of the contractile responses of aortic, carotid, and iliac arterial strips and vasa deferentia from 15- to 17-week-old spontaneously hypertensive rats (SHR) and their normotensive counterparts, Wistar Kyoto (WKY) rats. KCl-induced responses of the aorta from both strains of rats and carotid arteries from WKY only were more sensitive to inhibition than were responses to norepinephrine. No significant differences were observed in the inhibition of tissue responses from the two strains of rats with the exception of the K+-induced responses of carotid arterial strips from SHR which were significantly less sensitive to inhibition when compared with carotid strips from WKY.

Evidence for circulating factors as a cause of venous hypertrophy in spontaneously hypertensive rats

1981 ◽  
Vol 241 (3) ◽  
pp. H421-H430 ◽  
Author(s):  
S. Greenberg ◽  
K. Gaines ◽  
D. Sweatt
Keyword(s):  
Smooth Muscle ◽  
Spontaneously Hypertensive Rats ◽  
Muscle Hypertrophy ◽  
Dry Weight ◽  
Hypertensive Rats ◽  
Humoral Factors ◽  
Spontaneously Hypertensive ◽  
Blood Flows ◽  
Portal Veins ◽  
Wistar Kyoto

Increased contractility, decreased extensibility, and hypertrophy occur in portal veins (PV) obtained from spontaneously hypertensive rats (SHR). This study evaluates the potential existence of circulating humoral factors as mediators of these changes. SHR were parabiosed with normotensive Wistar-Kyoto rats (WKY) matched for sex and age. Blood pressure increased over a 3-wk to 5-mo period in 2-mo-old WKY parabiosed with SHR. Similar changes were absent in WKY parabiosed with WKY (WKY-WKY) or in SHR parabiosed with SHR (SHR-SHR). The functional blood flows between the parabiosed pairs were 1.4 +/- 0.21%. PV obtained from WKY-WKY developed less spontaneous tension, less tension in response to norepinephrine, potassium chloride, angiotensin II, an 9 alpha, 11 alpha-epoxymethano-prostaglandin H2, and were more extensible than PV obtained from SHR-SHR. In contrast, PV obtained from the WKY member of the WKY-SHR, developed changes similar to PV obtained from the SHR. The wet and dry weight and protein content increased in the PV of WKY-SHR, when compared with these parameters in the PV obtained from WKY-WKY. Light microscopy of the blood vessels demonstrated that PV obtained from the wKY parabiosed to SHR exhibited medial smooth muscle hypertrophy. These data support the conclusion that a circulating humoral factor in the SHR may initiate the venous smooth muscle derangements during the development of spontaneous hypertension.

Ouabain in plasma from spontaneously hypertensive rats

1994 ◽  
Vol 266 (1) ◽  
pp. H360-H364 ◽  
Author(s):  
P. A. Doris
Keyword(s):  
Inhibitory Activity ◽  
Spontaneously Hypertensive Rats ◽  
Sodium Pump ◽  
Calcium Content ◽  
Dietary Calcium ◽  
Dietary Calcium Intake ◽  
Hypertensive Rats ◽  
Uptake Inhibition ◽  
Spontaneously Hypertensive ◽  
Wistar Kyoto

Ouabain has recently been identified in mammalian plasma with an apparent adrenocortical origin. The objectives of the present study were to determine whether boiled plasma supernatants (BPS) from spontaneously hypertensive rats (SHR) contained elevated levels of material able to inhibit 86Rb uptake, an indicator of sodium pump activity, compared with Wistar-Kyoto rats (WKY). Furthermore, the effect of increasing dietary calcium content from 1 to 3% on 86Rb-uptake inhibitory activity in plasma was examined. BPS from SHR and WKY consuming 1% calcium contained sodium pump inhibitory activity equivalent to 16.43 +/- 0.23 and 5.08 +/- 0.10 ng ouabain/ml, respectively (P < 0.0001). Increasing dietary calcium intake to 3% reduced plasma ouabain-like activity (OLA) to 9.97 +/- 0.20 ng/ml (P < 0.0001) in SHR but was without effect in WKY (5.39 +/- 0.05; not significant). It was then determined whether the plasma 86Rb-uptake inhibition could be attributed to authentic ouabain. In WKY plasma pools the percentage of OLA attributable to authentic ouabain was 38.0% by radioimmunoassay and 56.7% by 86Rb-uptake assay. In SHR these values were 3.8% and < 7.1%, respectively. Whereas the data in the present study provide confirmation of the presence of ouabain in rat plasma, ouabain does not account for the elevated OLA in SHR plasma reported here and elsewhere. This hypertensinogenic cardiotonic steroid appears to be appropriately downregulated in SHR rats.

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