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- Franzen, Stephanie, et al.
(författare)
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Prevention of hemorrhage-induced renal vasoconstriction and hypoxia by angiotensin II type 1 receptor antagonism in pigs
- 2021
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Ingår i: American Journal of Physiology. Regulatory Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 321:1, s. R12-R20
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Tidskriftsartikel (refereegranskat)abstract
- Angiotensin II (ANG II) is a potent vasoconstrictor and may reduce renal blood flow (RBF), causing renal hypoxia. Hypotensive hemorrhage elevates plasma ANG II levels and is associated with increased risk of acute kidney injury. We hypothesized that ANG II antagonism prevents renal vasoconstriction and hypoxia caused by hemorrhage. Pigs were anaesthetized, surgically prepared, and randomized to intravenous losartan (1.5 mg center dot kg-1 center dot h-1, n = 8) or an equal volume of intravenous Ringer acetate (vehicletreated, n = 8). Hemorrhage was induced by continuous aspiration of blood to reach and sustain mean arterial pressure of <50 mmHg for 30 min. Plasma ANG II levels, hemodynamics and oxygenation were assessed 60 min prehemorrhage, 30-min after the start of hemorrhage, and 60 min posthemorrhage. Erythropoietin mRNA was analyzed in cortical and medullary tissue sampled at the end of the experiment. Hypotensive hemorrhage increased plasma ANG II levels and decreased RBF and oxygen delivery in both groups. Losartan-treated animals recovered in RBF and oxygen delivery, whereas vehicle-treated animals had persistently reduced RBF and oxygen delivery. In accordance, renal vascular resistance increased over time post hemorrhage in vehicle-treated animals but was unchanged in losartan-treated animals. Renal oxygen extraction rate and cortical erythropoietin mRNA levels increased in the vehicle group but not in the losartan group. In conclusion, ANG II antagonism alleviates prolonged renal vasoconstriction and renal hypoxia in a large animal model of hypotensive hemorrhage.
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| 2. |
- Frithiof, Robert, et al.
(författare)
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Intracarotid hypertonic sodium chloride differentially modulates sympathetic nerve activity to the heart and kidney
- 2014
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Ingår i: American Journal of Physiology. Regulatory Integrative and Comparative Physiology. - : American Physiological Society. - 0363-6119 .- 1522-1490. ; 306:8, s. R567-R575
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Tidskriftsartikel (refereegranskat)abstract
- Frithiof R, Xing T, McKinley MJ, May CN, Ramchandra R. Intracarotid hypertonic sodium chloride differentially modulates sympathetic nerve activity to the heart and kidney. Am J Physiol Regul Integr Comp Physiol 306: R567-R575, 2014. First published February 12, 2014; doi: 10.1152/ajpregu. 00460.2013.-Hypertonic NaCl infused into the carotid arteries increases mean arterial pressure (MAP) and changes sympathetic nerve activity (SNA) via cerebral mechanisms. We hypothesized that elevated sodium levels in the blood supply to the brain would induce differential responses in renal and cardiac SNA via sensors located outside the blood-brain barrier. To investigate this hypothesis, we measured renal and cardiac SNA simultaneously in conscious sheep during intracarotid infusions of NaCl (1.2 M), sorbitol (2.4 M), or urea (2.4 M) at 1 ml/min for 4 min into each carotid. Intracarotid NaCl significantly increased MAP (91 +/- 2 to 97 +/- 3 mmHg, P < 0.05) without changing heart rate (HR). Intracarotid NaCl was associated with no change in cardiac SNA (11 +/- 5.0%), but a significant inhibition of renal SNA (-32.5 +/- 6.4%, P < 0.05). Neither intracarotid sorbitol nor urea changed MAP, HR, central venous pressure, cardiac SNA, and renal SNA. The changes in MAP and renal SNA were completely abolished by microinjection of the GABA agonist muscimol (5 mM, 500 nl each side) into the paraventricular nucleus of the hypothalamus (PVN). Infusion of intracarotid NaCl for 20 min stimulated a larger increase in water intake (1,100 +/- 75 ml) than intracarotid sorbitol (683 +/- 125 ml) or intracarotid urea (0 ml). These results demonstrate that acute increases in blood sodium levels cause a decrease in renal SNA, but no change in cardiac SNA in conscious sheep. These effects are mediated by cerebral sensors located outside the blood-brain barrier that are more responsive to changes in sodium concentration than osmolality. The renal sympathoinhibitory effects of sodium are mediated via a pathway that synapses in the PVN.
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