A rabbit pulmonary vein myocyte isolation method based on simultaneous heart and pulmonary vein perfusion / 生理学报

Myocytes in the pulmonary veins (PV) play a pivotal role in the development of paroxysmal atrial fibrillation (AF). It is therefore important to understand physiological characteristics of these cells. Studies on these cells are, however, markedly impeded by the fact that single PV myocytes are very difficult to obtain due to lack of effective isolation methods. In this study, we described a novel PV myocyte isolation method. The key aspect of this method is to establish a combination of retrograde heart perfusion (via the aorta) and anterograde PV perfusion (via the pulmonary artery). With this simultaneous perfusion method, a better perfusion of the PV myocytes can be obtained. As results, the output and viability of single myocytes isolated by simultaneous heart and PV perfusion method were increased compared with those in conventional retrograde heart perfusion method.

Different signal molecules involved in the muscarinic modulation of pacemaker current I(f) on the heart of mouse embryo in different developmental stages / 生理学报

We isolated mouse embryonic cardiomyocytes derived from timed-pregnant females at different periods and used patch-clamp technique to investigate the muscarinic cholinergic modulation of pacemaker current I(f) in different developmental stages. In early development stage (EDS), muscarinic agonist carbachol (CCh) significantly decreased the magnitude of the pacemaker current I(f) but had no effect in late development stage (LDS). Forskolin (a direct adenylate cyclase activator) and IBMX (a non-selective phosphodiesterase inhibitor) increased I(f) in both EDS and LDS cells. Interestingly, although both forskolin and IBMX increased basal I(f), their effects on CCh-inhibited I(f) were different. Forskolin did not reverse the inhibitory action of CCh until intermediate development stage (IDS). In contrast, IBMX reversed the inhibitory action of CCh on I(f) in EDS but not in IDS. It is suggested that a decrease in intracellular cAMP is a possible mechanism for CCh to modulate I(f). During the EDS and IDS CCh controls the cytoplasmic cAMP level by different pathways: In EDS, CCh modulates I(f) possibly by activating PDE which accelerates the breakdown of cAMP, but in IDS possibly by inhibiting adenylate cyclase (AC) which then reduces the synthesis of cAMP.

Chronic intermittent hypoxia decreases acute hypoxic inhibition of voltage-gated potassium channel in rat pulmonary arterial smooth muscle cells / 生理学报

For determination the ionic mechanisms of the hypoxic acclimatization at the level of channels, male Spradue-Dawley rats were divided into two groups: control normoxic group and chronic intermittent hypoxic group [O2 concentration: (10 +/-0.5)%, hypoxia 8 h a day]. Using whole cell patch-clamp technique, voltage-gated potassium channel currents (IK(V)) were recorded in freshly isolated pulmonary arterial smooth muscle cells (PASMCs) of rat with acute isolated method. The effect of acute hypoxia on IK(V) of PASMCs from chronic intermittent hypoxia group was investigated to offer some basic data for clarifying the ionic mechanisms of the hypoxic acclimatization. The results showed: (1) In control normoxic group, after acute hypoxia free-Ca(2+) solution, the resting membrane potential (Em) of PASMCs was depolarized significantly from -47.2+/-2.6 mV to -26.7+/-1.2 mV, and the IK(V) of PASMCs was decreased significantly from 153.4+/-9.5 pA/pF to 70.1+/-0.6 pA/pF, the peak current percent inhibition was up to (57.6+/-3.3)% at +60 mV, and current-voltage relationship curve shifted to the right. (2) In chronic intermittent hypoxic group, the IK(V) of PASMCs was decreased significantly by exposure to intermittent hypoxia in a time-dependent manner, appeared to start on day 10 and continued to day 30 (the longest time tested) of hypoxia, and current-voltage relationship curve shifted to the right in a time-dependent manner. (3) Compared with the control normoxic group, the percent IK(V) inhibition by acute hypoxia was significantly attenuated in the chronic intermittent hypoxia group and this inhibition effect declined with time exposure to hypoxia. The results suggest that K(V) inhibition was significantly attenuated by chronic intermittent hypoxia, and this effect may be a critical mechanism of the body hypoxic acclimatization.