Retinol mobilization from retinyl esters stores of hepatic stellate cells (HSCs) is a key step in the regulation of mammalian retinol homeostasis, but the precise mechanisms of such a mobilization are still poorly understood. Using primary cultures of HSCs, we first demonstrated that HSCs expressed immunoreactivity against retinol-binding-protein (RBP) when cultured in a medium containing RBP but were unable to synthesize RBP transcripts and proteins. Using pulse and chase-type experiments, we demonstrated that radioactive retinol was released in culture medium without binding proteins. Inhibition of protein secretion by brefeldin A did not modify quantitatively retinol release. This data ruled out, for the first time, the direct involvement of RBP in retinol mobilization from HSCs. Moreover, HSCs co-cultured with primary isolated hepatocytes displayed an increase of retinol transfer from HSCs to hepatocytes when they established direct physical contacts, as compared with co-cultures without contact. Based on this latter data, a mechanism of retinol mobilization from HSCs via the hepatocytes using retinol transfer through cellular membranes is proposed.

Retinol mobilization from cultured rat hepatic stellate cells does not require retinol binding protein synthesis and secretion

COLANTUONI V;
2001-01-01

Abstract

Retinol mobilization from retinyl esters stores of hepatic stellate cells (HSCs) is a key step in the regulation of mammalian retinol homeostasis, but the precise mechanisms of such a mobilization are still poorly understood. Using primary cultures of HSCs, we first demonstrated that HSCs expressed immunoreactivity against retinol-binding-protein (RBP) when cultured in a medium containing RBP but were unable to synthesize RBP transcripts and proteins. Using pulse and chase-type experiments, we demonstrated that radioactive retinol was released in culture medium without binding proteins. Inhibition of protein secretion by brefeldin A did not modify quantitatively retinol release. This data ruled out, for the first time, the direct involvement of RBP in retinol mobilization from HSCs. Moreover, HSCs co-cultured with primary isolated hepatocytes displayed an increase of retinol transfer from HSCs to hepatocytes when they established direct physical contacts, as compared with co-cultures without contact. Based on this latter data, a mechanism of retinol mobilization from HSCs via the hepatocytes using retinol transfer through cellular membranes is proposed.
2001
hepatic stellate cells (HSCs); Retinoid mobilization
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.12070/5423
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