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α-adrenergic blockade prevented environmental temperature reduction-induced transient portal pressure surge in cirrhotic and portal hypertensive rats.

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Exposure to low temperatures has been associated with increased gastroesophageal variceal bleeding in patients with cirrhosis and portal hypertension, however the mechanism remains unclear. Therefore, the aim of this study… Click to show full abstract

Exposure to low temperatures has been associated with increased gastroesophageal variceal bleeding in patients with cirrhosis and portal hypertension, however the mechanism remains unclear. Therefore, the aim of this study was to evaluate the impact of environmental temperature reduction on portal hypertension and the role of adrenergic signaling pathways in this phenomenon. Male Sprague-Dawley rats underwent common bile duct ligation or partial portal vein ligation to induce liver cirrhosis and/or portal hypertension. The impacts of acute or chronic changes in environmental temperature were surveyed. The results showed that acute cooling from 25℃ to 15℃ and 5℃ increased the portal pressure by 10.6% and 15.5% in cirrhotic rats, and by 22.2% and 36.1% in portal hypertensive rats, respectively. The transient portal pressure surge started shortly after cooling, reached a peak within 5 minutes, and returned to baseline after 10 minutes. Systemic vascular resistance, mean arterial pressure and splanchnic blood flow increased significantly at the same time. Plasma epinephrine and norepinephrine concentrations, phospholipase C, protein kinase C activity and myosin phosphorylation of peripheral arteries increased significantly in response to cooling. Phentolamine (an α-blocker) but not propranolol (a non-selective β-blocker) dose-dependently inhibited the transient portal pressure surge and aforementioned molecular changes. In conclusion, environmental temperature reduction induced peripheral vasoconstriction via α-adrenergic pathways, and redistribution of blood flow to the splanchnic system led to a surge in transient portal pressure. Treatment with α-adrenergic receptor antagonists may exert additional benefits in controlling portal hypertension, especially on exposure to low temperatures.

Keywords: surge; transient portal; pressure; portal pressure; environmental temperature

Journal Title: Clinical science
Year Published: 2022

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