The association between KCNJ5 gene polymorphism and primary hyperaldosteronism / 中华内分泌代谢杂志

Objective To investigate the association between KCNJ5 gene polymorphism and primary hyperaldosteronism(PA).Methods A total of 248 PA patients and 816 essential hypertension (EH) patients were enrolled in this study,TaqMan assay was used to detect the rs1221497 polymorphism of KCNJ5 gene.Results The genotypes of rs1221497 were in Hardy-Weinberg equilibrium in both PA group and EH group,the genotype frequencies ofGG,GC,CC were 208,39,1 in PA group and 631,177,8 in EH group respectively,the allele frequencies in the two groups were 455,41 and 1 439,193 respectively.The frequencies of GG genotype and G allele in PA group were significantly higher than those in EH group.Logistic regression showed that GG genotype was closely associated with PA after adjusting age.Conclusions GG genotype and G allele may contribute to the occurrence of PA.

Regulation of Adenosine-activated GIRK Channels by Gq-coupled Receptors in Mouse Atrial Myocytes

Adenosine (Ado) is an important mediator of the endogenous defense against ischemia-induced injury in the heart. The action of Ado is mediated by activation of G protein-gated inwardly rectifying K+ (GIRK) channels. In turn, GIRK channels are inhibited by reducing phosphatidylinositol 4,5-bisphosphate (PIP2) through Gq protein-coupled receptors (GqPCRs). We previously found that GIRK channels activated by acetylcholine, a muscarinic M2 acetylcholine receptor agonist, are inhibited by GqPCRs in a receptor-specific manner. However, it is not known whether GIRK channels activated by Ado signaling are also regulated by GqPCRs. Presently, this was investigated in mouse atrial myocytes using the patch clamp technique. GIRK channels were activated by 100 micrometer Ado. When Ado was repetitively applied at intervals of 5~6 min, the amplitude of second Ado-activated GIRK currents (I(K(Ado))) was 88.3+/-3.7% of the first I(K(Ado)) in the control. Pretreatment of atrial myocytes with phenylephrine, endothelin-1, or bradykinin prior to a second application of Ado reduced the amplitude of the second I(K(Ado)) to 25.5+/-11.6%, 30.5+/-5.6%, and 96.0+/-2.7%, respectively. The potency of I(K(Ado)) inhibition by GqPCRs was different with that observed in acetylcholine-activated GIRK currents (I(K(ACh))) (endothelin-1>phenylephrine>bradykinin). I(K(Ado)) was almost completely inhibited by 500 micrometer of the PIP2 scavenger neomycin, suggesting low PIP2 affinity of I(K(Ado)). Taken together, these results suggest that the crosstalk between GqPCRs and the Ado-induced signaling pathway is receptor-specific. The differential change in PIP2 affinity of GIRK channels activated by Ado and ACh may underlie, at least in part, their differential responses to GqPCR agonists.

Modulation of Muscarinic K+ Channel by Protein Kinase C in Ischemic Rat Atrial Myocytes

BACKGROUND AND OBJECTIVES: Recent studies have shown that many kinds of K+ channels, including the muscarinic K+ channel (KACh), are activated in the ischemic heart. It is known that these channels can be modulated by phosphorylation. However, little is known about the function of the KACh in ischemic hearts. In this study, we examined whether the KACh channel is mediated by protein kinase C (PKC) activation in rat atrial myocytes under ischemic conditions. MATERIALS AND METHODS: Single atrial cells of adult rat heart were prepared by collagenase digestion. Channel activity of KACh was recorded by cell-attached configuration from single atrial cells under ischemic conditions, using a patch clamp technique. To simulate ischemia, adenosine or potassium cyanide (KCN) was applied to atrial myocytes, and Western blot was performed to specify PKC isoforms. RESULTS: Adenosine and KCN markedly increased KACh channel activity. The responses to adenosine and KCN were increased 3-fold at mean open time from that observed with control. Channel activity of KACh was blocked by pretreatment with PKC antagonists such as sphingosine, Go 6976, and rottlerin. PKC alpha and PKC betaI isoform levels were increased in the membrane fraction of ischemic heart, indicating that ischemic stress might trigger translocation of cytosolic PKC to the cell membrane. CONCLUSION: These results show that KACh channels are modulated by PKC activation under ischemic conditions induced by adenosine or KCN. Therefore, the channels can protect the heart from ischemic stress by increasing channel activity.

Effect of weaver gene on biology function of CAD cells / 中国病理生理杂志

AIM: To assess the impact of weaver gene on neuronal development,protein expression and vitality. METHODS: DNA encoding the wild-type and mutant ion channel was introduced into immortalized tyrosine hydroxylase-positive CNS-derived neurons named CAD(Cath.a-differentiated,a variant of Cath.a. Cath.a was established by targeted oncogenesis in transgenic mice) cells. DNA clone, immunostaining and Western blotting were used. Three different concentrations (0 25 mg/L, 0 5 mg/L, or 1 0 mg/L) of Girk2 and wv Girk2 expression plasmids were transfected into the CAD cells. The number of transfected cycling cells, protein synthesis and neurites growth were observed between two groups. RESULTS: The number of transfected cycling CAD cells with high concentration of wv Girk2 reduced to about 60%, compared to Girk2-transfected cells. Low concentration of wv Girk2 did not cause cell death but reduced the protein production of transfected genes. Neurite growth was also affected by wv Girk2. MK-801 and Kir2.3 altered the effect of wv Girk2. CONCLUSION: The results indicate that wv Girk2 functions as a blocker in weaver animals, which blockes the wv Girk2 channel to rescue the cells from death. Our data also suggest that the presence of channels and the level of wv Girk2 may have a significant impact on the fate of cells containing wv Girk2.