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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Contractile properties of isolated papillary muscles from three age groups of spontaeously hypertensive rats (SHRs) were compared to those from age-matched Wistar-Kyoto rats (WKYs) to assess whether there were differences between the strains preceding and during the course of the hypertension. In all three age groups (7, 12, and 50 wk), the mechanical refractory periods (MRP) were longer and aftercontractions more prominent after paired pulse stimulation in preparations from SHRs than from age-matched WKYs. Other isometric twitch properties of SHR papillary muscles at Lmax were not different from WKYs, with the exception of a shorter half-relaxation time in the youngest SHR group. Although hypertension and cardiac hypertrophy increased in SHRs with age, aging had similar influences on most cardiac contractile properties in both strains. None of the isometric properties of papillary muscles from rats made hypertensive by Doca treatment were different from those in normotensive control preparations. This suggests that differences seen between SHRs and WKYs probably represent genetic differences between these strains and are not directly caused by the hypertension.
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PMID:Cardiac muscle mechanics from Doca- and aging spontaneously hypertensive rats. 56 15

If the posterior hypothalamus contributes to elevate blood pressure in hypertension by increasing sympathetic vasomotor activity, then lesions of the posterior hypothalamus should lower blood pressure more in hypertensive than in normotensive rats. To test this hypothesis without complications caused by anaesthesia, aortic pressures were recorded from indwelling catheters in awake rats before and after selective hypothalamic destruction. In normotensive rats rats, bilateral lesions of the medial areas of the posterior hypothalamus always lowered blood pressure while those in the anterior hypothalamus slightly increased it. Heart rate responses varied widely and did not seem to contribute to the blood pressure changes. Posterior hypothalamic lesions of approximately the same size had significantly greater hypotensive after-effects in renal and spontaneously hypentensive rats than in normotensive or Doca hypentensive ones. These results imply that sympathetic overactivity emanating from posterior hypothalamic centres contributes to the blood pressure elevation in spontaneous or chronic renal hypentension but not in Doca hypertension. However, because of inherent weaknesses in the 'lesion method' and the complexity of blood pressure regulation in awake animals, other explanations are possible.
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PMID:Immediate hypotensive after-effects of posterior hypothalamic lesions in awake rats with spontaneous, renal, or Doca hypertension. 79 90

Salt consumption was compared in two strains of rats, selected for their disparate proneness (strain "H") or resistance (strain "N") to Doca-salt hypertension. NaCl intake was similar in "H" and "N" rats prior to an following administration of Doca, while their respective blood pressures at the end of this experiment was 178 +/- 5mm Hg vs. 134 +/- 3 mm Hg. Thus, disparate responses of the blood pressure to Doca in the two strains cannot be ascribed to differences in salt intake. In another study, salt preference was tested in "H" and "N" rats by two-bottle self-selecting technique. Before Doca, saline preference in "H" rats averaged 60.3 +/- 5.8% of total daily fluid consumption, vs 18 +/- 4.2% in "N" rats. Following Doca treatment for 3 weeks the respective values were 96 +/- 1.7% vs 67 +/- 6.6%. Thus Doca treatment enhanced salt appetite in both strains, but salt preference remained significantly higher in the "H" rats. The increased susceptibility to hypertension and enhanced salt appetite in the "H" rat, corroborates similar reports in the Okamoto "SH" rat. In the Brookhaven "S" rat, however, susceptibility to hypertension is associated with salt avoidance. The conflicting data do not support a unified concept of a genetically determined link between salt appetite and proneness to hypertension.
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PMID:Sodium chloride preference in hypertensive (H) and normotensive (N) rats. 94 89

The handling of an intraperitoneal NaCl load (2% body weight, 0.9% NaCl) administered twice a week during DOCA-salt and Goldblatt 2K-1C hypertension development has been evaluated. An exaggerated natriuresis was observed in DS-hypertensive rats since blood pressure became higher with respect to normal (C), Doca (D) and uninephrectomized-salt (NS) rats that served as controls. However, this phenomenon was not observed in Goldblatt 2K-1C hypertensive rats (2K-1C) when compared to the response obtained in sham-operated (SO) rats. These results suggest that: 1) An increased blood pressure, per se, is not a determinating factor for exaggerated natriuresis. 2) Rise in blood pressure and exaggerated natriuresis may be related through a common mechanism in Doca-salt hypertension.
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PMID:The handling of NaCl load in rats during DOCA-salt and Goldblatt 2 kidney-1 clip hypertension development. 319 75

Distinct differences in central and peripheral noradrenaline (NA) were observed in the hypertension prone (SBH) and resistant (SBN) strain, derived from the Hebrew University SABRA rats. In the medulla oblongata NA concentration was 90% higher and tyrosine hydroxylase activity 88% lower in SBN when compared to SBH, suggesting marked strain differences in NA turnover. In this area, NA-induced cAMP generation was higher in SBH than in SBN, while the hypothalamus, the reverse situation was present. The relevance of hypertension of the reciprocal cAMP changes is still uncertain. The concentration of NA in heart tissue was significantly higher in SBN than in SBH. Doca-salt treatment caused hypertension and depletion of atrial NA in SBH, but had no effect on either blood pressure or atrial NA in SBN rats. The results suggest that resistance to hypertension in SBN rats is associated with decreased NA turnover in medulla oblongata and reduced activity of cardiac neuronal sympathetic endings.
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PMID:Distinguishing traits in the Sabra hypertension-prone (SBH) and hypertension-resistant (SBN) rats. 611 32

The present study was conducted to measure norepinephrine release during sympathetic nerve stimulation and to evaluate vascular reactivity in the isolated perfused mesenteric vasculature of normotensive and Doca-salt hypertensive rats. Significantly greater vasoconstrictor responses to periarterial nerve stimulation, norepinephrine, and vasopressin, but not to barium chloride, were observed in the mesenteric vasculature of the hypertensive rats in comparison with the control normotensive group. Norepinephrine release, measured as total tritium overflow, during periarterial nerve stimulation at 4 Hz for 2 min, was identical in both normotensive and hypertensive animals. Phentolamine (5.3 micro M) significantly increased tritium overflow, but to the same extent in the normotensive and the hypertensive mesenteric vasculature, suggesting that the negative feedback presynaptic alpha-adrenoceptor mechanism, which has been proposed to modulate transmitter release, was unaltered in this form of hypertension. These results indicate that hyperresponsiveness of the mesenteric vasculature to periarterial nerve stimulation in the hypertensive rats is due to increased sensitivity of the vascular alpha-adrenoceptor and not facilitation of the transmitter release. The increased vascular reactivity to norepinephrine and vasopressin may be involved in the maintenance of Doca-salt hypertension.
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PMID:Sympathetic nerve function and vascular reactivity in Doca-salt hypertensive rats. 625 76

Uni-nephrectomized rats drinking 1% saline instead of water, were given Doca intramuscularly, 50 mg/kg BW per week for 2 weeks. The mean blood pressure in the control group was 105 +/- 4 (+/- S.E.) mm Hg, whereas in the Doca-saline group it rose to 152 +/- 5.1 (p less than 0.001). Rats, similarly treated, were placed on daily intraperitoneal lithium injections of either of two doses: 1.5 or 3.0 mEq/kg BW per day. Their blood pressures, at the end of 2 weeks of treatment, were 117 +/- 2 mm Hg and 103 +/- 2.1, respectively (p less than 0.001 vs. lithium-untreated Doca-saline rats). Water-drinking rats, receiving daily intraperitoneal lithium (3 mEq/kg BW) for 2 weeks, had normal blood pressures, not different from the controls (104 +/- 11 mm Hg). The Doca-saline and Doca-saline-lithium (1.5 mEq/kg/day) groups had similar changes in mean daily body weight, plasma sodium, osmolality, and GFR. The renal beta-adrenergic receptor density in the Doca-saline-lithium rats was in the normal range, 51 +/- 4.5 mol/mg of protein. In the Doca-saline hypertensive rats, it was significantly lower, being 27.2 +/- 3 fmol/mg of protein, p less than 0.05. These renal plasma cell membrane beta-adrenergic receptors were characterized by direct tissue binding with (-)[3H]dihydroalprenolol. These results show that lithium prevents the development of hypertension in the Doca-saline rats. The effect of lithium on the sympathetic nervous system is a possible mechanism in the prevention of the Doca-saline hypertension.
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PMID:Lithium prevents saline deoxycorticosterone acetate (DOCA) hypertension in the rat. 627 37