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Lactate production by BHK cells is stimulated by arsenite, azide, or by infection with Semliki Forest virus (SFV). In the case of arsenite or SFV infection, the increase correlates approximately with the increase in glucose transport as measured by uptake of [3H] deoxy glucose (dGlc); in the case of azide, the increase in lactate production exceeds that of glucose transport. Hence glucose utilization by BHK cells and its stimulation by anaerobic and other types of cellular stress is controlled at least in part at the level of glucose transport. The glucose uptake by BHK cells is also stimulated by serum and by glucose deprivation. In these circumstances, as with arsenite, stimulation is reversible, with t1/2 of 1-2 hours; stimulation is compatible with a translocation of the glucose transporter protein between an intracellular site and the plasma membrane (shown here for serum and previously for arsenite). The surface binding and rate of internalization of [125I]-labelled transferrin and [125I] alpha 2-macroglobulin was studied to determine whether changes in glucose transport are accompanied by changes in the surface concentration or rate of internalization of membrane proteins. The findings indicate that changes in glucose transport do not reflect a consistent and general redistribution of membrane receptors. Taken together, the results are compatible with the proposal that BHK cells exposed to stimuli like insulin or serum, or to stresses like arsenite, azide, SFV infection, or deprivation of glucose, respond in the same manner: namely, by an increased capacity to transport glucose brought about by reversible and specific translocation of the transporter protein from an (inactive) intracellular site to the plasma membrane.

Western blots immunostained for the basolateral Na ؉ -dependent plasma membrane protein, ntcp, revealed the appropriate Ϸ50-kd band in control and TC-grown cells, and confocal immunofluorescence microscopy demonstrated staining along the basolateral plasma membrane. Northern blots hybridized with a cDNA probe directed against ntcp indicated a modest TC-induced increase in mRNA levels. Reverse-transcriptase polymerase chain reaction (RT-PCR) using RNA isolated from WIF-B cells and oligonucleotide primers specific for rat ntcp or human NTCP transcripts revealed only the presence of the rat ntcp transcript. We conclude that bile salts, at concentrations normally found in mammalian portal blood, may be capable of promoting enhanced hepatocellular bile salt uptake via an increase in basolateral Na ؉ -dependent plasma membrane transport capacity. (HEPATOLOGY 1998;27:191-199.)The mammalian liver is continually exposed to low concentrations of bile salts present in portal and peripheral blood. Hepatocytes avidly take up bile salts across the basolateral plasma membrane and rapidly secrete them into bile; less than 5% of secreted bile salts are derived from de novo synthesis within the hepatocyte. 1 In rats, the postprandial bile salt concentration in the portal blood is Ϸ60 µmol/L, with taurocholate (TC) comprising up to half of the bile salt species. 2 In humans, the bile salt load reaching the liver fluctuates considerably over a 24-hour period, with portal vein plasma concentrations ranging from Ϸ14 µmol/L in the fasting state to Ϸ43 µmol/L in the postprandial state. 3 Hepatocytes are thus exposed routinely to changes in rates of bile salt delivery, and therefore must respond with variable rates of bile salt uptake across the basolateral plasma membrane. High plasma bile salt concentrations (up to 1 mmol/L) are associated with down-regulation of basolateral bile salt uptake into hepatocytes. 4 It is unclear, however, whether plasma bile salt concentrations within physiological ranges may promote bile salt uptake into hepatocytes.Difficulties are encountered when examining the physiological role of bile salts in intact animals, because many variables change simultaneously when conducting in vivo studies. A major experimental problem also is encountered when addressing normal bile salt regulation of hepatic physiology in vitro, because of the difficulty in maintaining liver preparations with stable rates of basolateral bile salt uptake. Isolated perfused rat livers maintain physiological rates of bile salt uptake and secretion for up to 3 hours, but bile flow decreases thereafter. 5 Isolated rat hepatocytes exhibit profound decreases in rates of bile salt uptake over the first 72 hours of primary culture. [6][7][8] Bile salt transport may be virtually absent in cultured hepatocyte tumor cell lines. 9 Recently, an in vitro polarized hepatocyte cell system, WIF-B cells, has been reported by Hubbard et al. 10,11 as a refinement of an existing rat hepatoma-human fibroblast cell line developed by Cassio et al. 12 WIF-B cell...

The peptide hormone relaxin is well-known for its anti-fibrotic actions in several organs, particularly from numerous studies conducted in animals. Acting through its cognate G proteincoupled receptor, relaxin family peptide receptor 1 (RXFP1), serelaxin (recombinant human relaxin) has been shown to consistently inhibit the excessive extracellular matrix production (fibrosis) that results from the aberrant wound-healing response to tissue injury and/or chronic inflammation, and at multiple levels. Furthermore, it can reduce established scarring by promoting the degradation of aberrant extracellular matrix components. Following on from the review that describes the mechanisms and signaling pathways associated with the extracellular matrix remodeling effects of serelaxin (Ng et al., 2019), this review focuses on newly identified tissue targets of serelaxin therapy in fibrosis, and the limitations associated with (se)relaxin research.

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