Down‐Regulation of Organic Anion Transporter 2 mRNA Expression by Nitric Oxide in Primary Cultured Rat Hepatocytes

Abstract

SummaryRole of nitric oxide (NO) 1 on the expression of organic anion transporter 2 (OAT2) located in sinusoidal domain of hepatocytes has been investigated. Effect of NO generated in vivo in rat and delivered in vitro to hepatocytes was determined. Lipopolysaccharide (LPS) and spermine NONOate (SPER/NO) were selected as the NO donors for in vivo and in vitro experiments, respectively. Constitutive basal expression of rOAT2 mRNA was detected in the normal rat liver and the level of its expression was decreased by intraperitoneal administration of LPS. This LPS-induced decrement did not occur when aminoguanidine (AG), an inhibitor of iNOS, was co-administered with LPS. The expression of rOAT2 mRNA was detected in hepatocytes, but not in the nonparenchymal cells. In the primary cultured hepatocytes obtained from normal rats (normal hepatocytes), a time-dependent decline of rOAT2 mRNA expression was observed, but not in the hepatocytes obtained from rats pretreated with gadolinium chloride (GdCl 3 , Gd-hepatocytes), an inhibitor of Kupffer cell activation. The decline of rOAT2 mRNA expression observed in the normal hepatocytes was enhanced by LPS treatment, but not in the Gd-hepatocytes. The LPS-dependent enhancement in the decline of rOAT2 mRNA expression did not occur when the normal hepatocytes were treated with AG or actinomycin D. When the Gd-hepatocytes were treated with SPER/NO, an NO donor, the rOAT2 mRNA expression declined markedly. Com-

Divergent Effects of Nitric Oxide Donors on the Biliary Efflux Transporters in Isolated Perfused Rat Livers: Nitric Oxide-Independent Inhibition of ABC Transporters by Sodium Nitroprusside

“…The limited literature dealing with the effects of NO on the hepatic transporters suggests that the effect may be at the transcriptional level [17][18][19], altering mRNA of the transporters, or via a direct interaction with the transporters [21], altering their activities. Although the transcriptional/ translational level are normally associated with some delay in appearance, the direct interactions could potentially result in changes in the activity of the transporter in a much shorter time.…”

“…Recent in vivo and in vitro studies have suggested that NO may play an important role in the regulation of the expression or activity of various liver transporters [17][18][19][20][21]. Most of these studies [17,19,20] used bacterial lipopolysaccharide (LPS) to induce upregulation of NO release. However, LPS also increases the proinflammatory cytokines, which are also known to affect the hepatic influx and efflux transporters [22,23].…”

Evidence for Heme Oxygenase‐1 Association with Caveolin‐1 and ‐2 in Mouse Mesangial Cells

“…The condition for PCR was as follows; one cycle of 1 min at 948C, 35 cycles each for 30 s at 948C, 30 s at 558C and 90 s at 728C, and one cycle of 10 min at 728C. The PCR products (15 ml) were then separated in a 1% agarose gel electrophoresis and stained with ethidium bromide (20). The sets of primers used for PCR amplification are shown in Table 1.…”

Interaction of Ethambutol with Human Organic Cation Transporters of the SLC22 Family Indicates Potential for Drug-Drug Interactions during Antituberculosis Therapy

“…hOCT1 and hOCT3 are both expressed in the sinusoidal membrane (blood side) of hepatocytes ( Fig. 2) and represent the first step in the hepatic excretion of many substances (12,15). In the kidney (Fig.…”