Comparison of the pacemaker current in canine sino-atrial node cells and the wild type mHCN2 pacemaker current in neonatal rat myocardial cells / 中华老年医学杂志

Objective To investigate the dynamic characteristics of the pacemaker current of canine sino-atrial node cells and compare them with the wild type mHCN2 pacemaker current overexpressed in neonatal rat myocardial cells.Methods Fresh canine sino-atrial node cells were enzymatically isolated in a calcium-free solution containing collagenase and elastase,and the funny current was recorded and compared with the mHCN2 current overexpressed in cultured neonatal rat myocardial cells under the same experimental conditions.Results The canine sinus node cells were elongated,spindle-shaped or polygonal,with well-defined boundaries,and showed spontaneous beating.The elicited pacemaker current was an inward current and its rise in amplitude quickened as the hyperpolarization potential increased.At V ＝-75 mV,the canine sinus atrial node pacemaker current was (-2.1±0.3) pA/pF and had the same activation kinetics as those of the mHCN2 channel current overexpressed in neonatal rat myocardial cells [τact:(728±137) ms vs.(530±65) ms,P＞0.05].Conclusions Within the physiological range,the pacemaker current in canine sino-atrial node cells and the wild type mHCN2 pacemaker current over expressed in neonatal rat myocardial cells have similar activation kinetics.

Gender-Related Differences in a Process of the Age-Dependent Alterations of the Elements in Monkey Sino-Atrial Node

Gender differences in the trace elements of monkey sino-atrial (SA) node were investigated in a process of age-dependent alterations. Sixty hearts from Japanese and rhesus monkeys (30 male and 30 female) used were aged ranging from 1-day- to 30-year-old. The elements were analyzed using an inductively coupled plasma-atomic emission spectrometer (ICP-AES). Advancing age decreased all the trace elements. Ca, P, S and Mg significantly decreased. The correlation coefficients of Ca and P were -0.178+/-0.081 (p<0.05) and -0.088+/-0.022 (p<0.05) in male (n=30), and -0.095+/-0.026 (p<0.05) and -0.069+/-0.017 (p<0.05) in female (n=30), respectively. The age-dependent coefficients for Fe/Ca, Zn/Ca, Fe/P, Fe/S, Zn/S, Fe/Mg and Zn/Mg were exhibited markedly in male, but all was less in female. In gender-related differences, only a ratio of P/Ca (p<0.05) was significantly observed with ageing. The trace elements such as Cu, Se and Sn were less detected in the SA nodes. These results indicate that the age-dependent changes in the ratios of elements are appeared more rapidly in male monkey SA node, and the gender difference is observed in ratio of P/Ca. The different attenuations may be involved with the age- and gender-related SA nodal functions.

Effects of cyclic-GMP on hyperpolarization-activated inward current (I|f) in sino-atrial node cells of rabbit

The aim of present study is to investigate the effects of cGMP on hyperpolarization activated inward current (If), pacemaker current of the heart, in rabbit sino-atrial node cells using the whole-cell patch clamp technique. When sodium nitroprusside (SNP, 80 muM), which is known to activate guanylyl cyclase, was added, If amplitude was increased and its activation was accelerated. However, when If was prestimulated by isopreterenol (ISO, 1 muM), SNP reversed the effect of ISO. In the absence of ISO, SNP shifted activation curve rightward. On the contrary in the presence of ISO, SNP shifted activation curve in opposite direction. 8Br-cGMP (100 muM), more potent PKG activator and worse PDE activator than cGMP, also increased basal If but did not reverse stimulatory effect of ISO. It was probable that PKG activation seemed to be involved in SNP-induced basal If increase. The fact that SNP inhibited ISO-stimulated If suggested cGMP antagonize cAMP action via the activation of PDE. This possibility was supported by experiment using 3-isobutyl-1-methylxanthine (IBMX), non-specific PDE inhibitor. SNP did not affect If when If was stimulated by 20 muM IBMX. Therefore, cGMP reversed the stimulatory effect of cAMP via cAMP breakdown by activating cGMP-stimulated PDE. These results suggest that PKG and PDE are involved in the modulation of If by cGMP: PKG may facilitate If and cGMP-stimulated PDE can counteract the stimulatory action of cAMP.

EVALUATION OF SINO-ATRIAL NODE FUNCTION IN CHILDREN BY TRANSESOPHAGEAL ATRIAL PACING / 重庆医科大学学报

Transesophageal atrial pacing was performed for evaluation sino-atrial node function in 102 normal children aged 2-15 years. These cases were evaluation again to make a controlled study after autonomic nerve blockade with propranolol(0.1mg/kg)and atropin(0.02mg/kg). In the group, values of SCL, SNRT, CSNRT, SNRTI declined significantly after autonomic blockade comparing with that before(P

LIGHT MICROSCOPIC OBSERVATION ON THE SINO-ATRIAL NODE OF THE DOG / 西安交通大学学报(医学版)

The sino-atrial node was observed in 23 dog hearts with serial slices. The sino-atrial node lies below auriculocaval junction, beneath the epicardium of sinus venosus by the side of the sulcus terminalis. The shape of the sino-atrial node is a long spindle with a greater upper part and a thiner lower part. Its central area is located near the junction of upper 1/3 and middle 1/3. Its size is 11.06?2.95?1.16mm, The sinoatrial node artery penetrates through the sino-atrial node only in 6 cases. In others, it may be located in sinus venosus side, the atrial side of the node or in the deep myocarium. Within the sino-atrial node there are chiefly P-cell ane T-cells. The P cell is small with greater nuclear, light colored, and formes clusters which present themselves in the centre of the sino-atrial node. The size of the T cell is between P cell and the myocardial working cell and is situated on the peripery of the sino-atrial node. In the sino-atrial node there are large numbers of collagen fibers. The nerve fiber ls appear more abundant near the lower part of the sino-atrial node.