Possible involvement of protein kinase C with induction of haptoglobin in cows by treatment with dexamethasone and by starvation

Kazuhiro Yoshino From the Department of Veterinary Biochemistry (Yoshino, Yuasa) and Veterinary Internal Medicine (Takahashi), Rakuno Gakuen University, Ebetsu 069, Japan, and Hokkaido Branch Laboratory, National Institute of Animal Health, Hitsujigaoka 4, Sapporo 062, Japan (Katoh).

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Norio Katoh From the Department of Veterinary Biochemistry (Yoshino, Yuasa) and Veterinary Internal Medicine (Takahashi), Rakuno Gakuen University, Ebetsu 069, Japan, and Hokkaido Branch Laboratory, National Institute of Animal Health, Hitsujigaoka 4, Sapporo 062, Japan (Katoh).

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Kiyoshi Takahashi From the Department of Veterinary Biochemistry (Yoshino, Yuasa) and Veterinary Internal Medicine (Takahashi), Rakuno Gakuen University, Ebetsu 069, Japan, and Hokkaido Branch Laboratory, National Institute of Animal Health, Hitsujigaoka 4, Sapporo 062, Japan (Katoh).

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Akira Yuasa From the Department of Veterinary Biochemistry (Yoshino, Yuasa) and Veterinary Internal Medicine (Takahashi), Rakuno Gakuen University, Ebetsu 069, Japan, and Hokkaido Branch Laboratory, National Institute of Animal Health, Hitsujigaoka 4, Sapporo 062, Japan (Katoh).

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Summary

Haptoglobin (Hp), an acute-phase protein, is detected in serum of cows with hepatic lipidosis (fatty liver). To assess the relevance of Hp in fatty liver, induction of Hp was examined, using conditions similar to those involving development of fatty liver in cows. Induction of Hp was achieved by a combination of dexamethasone administration (0.1 mg/kg of body weight) and 2 days’ starvation. Haptoglobin appearance in serum was not associated with the increase of α1-acid glycoprotein (a marker for inflammation). This treatment increased serum nonesterified fatty acids concentration and decreased serum triglycerides concentration. Protein kinase C activity was decreased in the cytosolic fractions of liver and mononuclear cells. Reduction of protein kinase C-catalyzed endogenous protein phosphorylation also was observed, particularly in the cytosolic fractions of the tissue and cells. Detection of Hp in serum of cows with fatty liver appears to be explained by the fact that Hp is induced by dexamethasone administration and starvation, which are similar to the condition responsible for fatty liver development. The change of protein kinase C-catalyzed phosphorylation was suggested to be involved in the induction of Hp in cows.

Summary

Haptoglobin (Hp), an acute-phase protein, is detected in serum of cows with hepatic lipidosis (fatty liver). To assess the relevance of Hp in fatty liver, induction of Hp was examined, using conditions similar to those involving development of fatty liver in cows. Induction of Hp was achieved by a combination of dexamethasone administration (0.1 mg/kg of body weight) and 2 days’ starvation. Haptoglobin appearance in serum was not associated with the increase of α1-acid glycoprotein (a marker for inflammation). This treatment increased serum nonesterified fatty acids concentration and decreased serum triglycerides concentration. Protein kinase C activity was decreased in the cytosolic fractions of liver and mononuclear cells. Reduction of protein kinase C-catalyzed endogenous protein phosphorylation also was observed, particularly in the cytosolic fractions of the tissue and cells. Detection of Hp in serum of cows with fatty liver appears to be explained by the fact that Hp is induced by dexamethasone administration and starvation, which are similar to the condition responsible for fatty liver development. The change of protein kinase C-catalyzed phosphorylation was suggested to be involved in the induction of Hp in cows.

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