Pacemaker currents modulated by C-type natriuretic peptide in interstitial cells of Cajal from murine small intestine

ABSTRACT

Although the presence of C-type natriuretic peptide (CNP) in gastrointestinal tract has been demonstrated, the effect of CNP on interstitial cells of Cajal (ICC), pacemaker cells in gastrointestinal tract, is still unclear. This study was designed to investigate the effect of CNP on pacemaker currents of ICC and possible mechanisms. We used immunocytochemistry techniques to exhibit natriuretic peptide receptors (NPR) and recorded membrane currents by using whole-cell patch clamp technique on cultured ICC. Our experiment showed that NPR-A and NPR-B were expressed in ICC from murine small intestine. Whole cell recordings further showed that the amplitude of pacemaker currents in intestinal small networks of ICC was 322±22pA and the frequency was 16.25±0.95 Hz. CNP significantly reduced the amplitude of pacemaker currents in small networks of ICC in a dose-dependent manner, and the amplitude was inhibited by 23.95%, 61.76% and 81.67%, the amplitude values in 329±28.0pA, 311.2±14.8pA and 295±26.5pA before treatment with CNP and 237.9±27.5pA, 119.6±18.5pA and 57.2±13.5pA after treatment with 0.01μmol•L−1, 0.1μmol•L−1 and 1μmol•L−1 CNP, respectively. The frequencies of pacemaker currents were also significantly reduced from 16.25±0.95Hz of control to 13±0.9Hz, 12±0.8Hz and 3±0.2Hz by 0.01μmol•L−1, 0.1μmol•L−1 and 1μmol•L−1 CNP, respectively. CNP also inhibited the amplitude of pacemaker currents in single ICC. The inhibitory effect of CNP was mimicked by 8-Br-cGMP, a membrane permeable cGMP analogue, which suggests that CNP could inhibit pacemaker currents via NPR-B-particulate guanylate cyclase (pGC)-cGMP signal pathway (AU)

RESUMEN

Se ha demostrado la presencia del péptido natriurético de tipo C (CNP) en tracto gastrointestinal. En el presente trabajo se investiga acerca del efecto del CNP sobre la actividad marcapaso en las células intersticiales de Cajal (ICC). Se utilizan técnicas de inmunohistoquímica para detectar receptores del péptido natriurético y se registran corrientes de membrana mediante la técnica de voltaje impuesto. Los resultados muestran la presencia de receptores NPR-A y NPR-B en ICC de intestino delgado de ratón. La amplitud de las corrientes marcapasos en pequeñas redes de ICC en intestino es de 322±22 pA y la frecuencia, de 16,25±0,95 Hz. El péptido CNP reduce la amplitud de la corriente marcapasos de ICC de modo dependiente de la concentración (en un 23,9%, 61,76% y 81,67% para concentraciones de CNP 0,01 μmol L−1, 0,1 μmol L−1 y 1 μmol L−1 respectivamente). También disminuyeron las frecuencias (desde el valor control 16,25±0,95 a 13±0,9 Hz, 12±08 Hz y 3±0,2 Hz para CNP 0,01 μmol L−1, 0,1 μmol L−1 y 1 μmol L−1 respectivamente). También se observa inhibición de la amplitud de las corrientes marcapaso por CNP en células ICC aisladas. El efecto inhibitorio del CNP es mimetizado por 8-Br-GMPc, un análogo permeable del GMPc, lo que sugiere que el CNP podría inhibir las corrientes marcapaso por interacción con NPR-B vía GMPc (AU)