The Effects of Puerarin on Rat Ventricular Myocytes and the Potential Mechanism

Puerarin, a known isoflavone, is commonly found as a Chinese herb medicine. It is widely used in China to treat cardiac diseases such as angina, cardiac infarction and arrhythmia. However, its cardioprotective mechanism remains unclear. In this study, puerarin significantly prolonged ventricular action potential duration (APD) with a dosage dependent manner in the micromolar range on isolated rat ventricular myocytes. However, submicromolar puerarin had no effect on resting membrane potential (RMP), action potential amplitude (APA) and maximal velocity of depolarization (Vmax) of action potential. Only above the concentration of 10 mM, puerarin exhibited more aggressive effect on action potential, and shifted RMP to the positive direction. Millimolar concentrations of puerarin significantly inhibited inward rectified K+ channels in a dosage dependent manner, and exhibited bigger effects upon Kir2.1 vs Kir2.3 in transfected HEK293 cells. As low as micromolar range concentrations of puerarin significantly inhibited Kv7.1 and IKs. These inhibitory effects may due to the direct inhibition of puerarin upon channels not via the PKA-dependent pathway. These results provided direct preclinical evidence that puerarin prolonged APD via its inhibitory effect upon Kv7.1 and IKs, contributing to a better understanding the mechanism of puerarin cardioprotection in the treatment of cardiovascular diseases

Molecular chaperones in the brain endothelialbarrier: neurotoxicity or neuroprotection?

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Hot Dust Close to the Young Massive Star Herschel 36

. The O7 star Herschel 36 is responsible for the ionisation of the "hourglass" region in M 8. Adaptive optics near-infrared observations with ADONIS confirmed its association with compact diffuse emission. This feature is most likely due to scattered light and thermal radiation from dust grains which are situated very close to the massive star. Mid-infrared and radio continuum observations strongly support this view. These findings are discussed in the framework of possible explanations: - Another proplyd-type object close to Herschel 36, - A deeply embedded massive protostar close to the line of sight towards Herschel 36, - Disk debris left from the formation of the high-mass star, - An evaporating gaseous globule close to the O star. 1 Introduction Herschel 36 (Her 36, HD 164740) is the most massive member of the young star cluster NGC 6523 situated in the western part of the Hii region M 8, the Lagoon Nebula. It is of spectral type O7V (Woolf 1961) and responsible for the ionisatio..