Demonstration of functional dipeptide transport with expression of PEPT2 in guinea pig cardiomyocytes

Abstract

The transporters PEPT1 and PEPT2 accept a broad spectrum of substrates including small, naturally occurring peptides and peptidomimetic drugs. This study aimed to investigate for the first time whether these transporters are expressed and active in isolated cardiomyocytes. PEPT1/PEPT2 expression in rat kidney (positive control), guinea pig kidney and cardiomyocytes were investigated by reverse transcription polymerase chain reaction. L-Glycyl-L-[(14)C]sarcosine (Gly-sar) uptake was characterised using freshly isolated suspensions of adult male guinea pig cardiomyocytes. PEPT2-specific primers recognised mRNA of appropriate size and sequence in cardiomyocytes and kidney, whilst PEPT1 was expressed in the kidney only. The initial uptake (30 s) of 200 microM Gly-sar was dependent on extracellular pH with a maximum at pH 6.0 (237.8 +/- 12.2 pmol/microl) and a minimum at pH 8.0 (72.1 +/- 13.4 pmol/microl, n = 6 +/- SE, p < 0.01, T test). The K (m) and V (max) of Gly-sar uptake at pH 6.0 were 495.5 +/- 69.6 microM and 1470.5 +/- 69.6 pmol microl(-1) min(-1). The addition of 10 mM fosinopril, cefadroxil, carnosine, cyclacillin or a variety of L-amino acid containing dipeptides/tripeptides significantly reduced Gly-sar uptake. Gly-sar uptake was not affected by 10 mM D-ala-D-ala, glycine or sarcosine. These results support the presence of a functional dipeptide transporter in isolated cardiomyocytes, with accompanying expression of PEPT2.

Proton-Coupled Oligopeptide Transporter (POT) Family Expression in Human Nasal Epithelium and Their Drug Transport Potential

“…In most reported studies with peptide transporters, metabolically stable dipeptides or dipeptide derivatives, especially Gly-Sar, Ala-Lys-AMCA and β-Ala- l -histidine, were used to characterize peptide transport in various epithelia. − In the present study, we chose Ala-Lys-AMCA and β-Ala- l -histidine as our model peptides for two reasons. First, studies involving radioactive tracers were not allowed on the floor level where our laboratory is located.…”

Physiology and Pathophysiology of Carnosine

“…Also other glia, such as astrocytes, seem to primarily depend on PEPT2 for their uptake of carnosine (393). Equally, other cell types such as cardiomyocytes (233) and epithelial tissues (human nasal epithelium) have been shown to express PEPT2, along with the other POTs, and to possess the ability to transport carnosine (6). The latter finding may have importance as a potential route to administer carnosine or carnosine-related drugs.…”

Role of l-carnosine in the control of blood glucose, blood pressure, thermogenesis, and lipolysis by autonomic nerves in rats: involvement of the circadian clock and histamine

“…The highaffinity type H ? /peptide cotransporter 2 (PEPT2) may be involved in the transport of CAR in the rat cerebellum (Fujita et al 1999), choroid plexus epithelial cells (Teuscher et al 2004;Hu et al 2005), astrocytes (Bauer 2005;Xiang et al 2006), cardiomyocytes (Lin and King 2007), and kidney (Jappar et al 2009;Kamal et al 2009). Moreover, PHT1, which may also mediate CAR transport, is observed throughout the whole brain (Yamashita et al 1997).…”