title: Long‑term treatment of spontaneously hypertensive rats with losartan and molecular basis of modulating Ito of ventricular myocytes.
abstract: The present study aimed to determine the effect of chronic treatment with losartan on transient outward potassium current (Ito) and the expression levels of potassium voltage-gated channel subfamily D members 2 and 3 (Kv4.2 and 3) and voltage-gated potassium channel-interacting protein 2 (KChIP2) in rats. Spontaneously hypertensive (SH) rats and Wistar-Kyoto (WKY) rats were used in the study. The rats were divided into lo-SH and SH groups and los-WKY and WKY groups, respectively. Ito was recorded and expression levels of Kv4.2, Kv4.3 and KChIP2 were measured by western blot analysis and quantitative polymerase chain reaction. Ito current density was smaller in SH compared with WKY, los-WKY and los-SH groups (P<0.01). Inactivation time constant of myocytes was larger in SH compared with WKY, los-WKY and los-SH groups (P<0.01). The mean levels of mRNA and protein of Kv4.2 and Kv4.3 were significantly lower in the SH compared with WKY, los-WKY and los‑SH groups in vivo and in vitro (P<0.01). The Pearson statistical test showed no correlation between the expression levels of Kv4.2, Kv4.3, KChIP2 and the changes in blood pressure in the losartan treatment group. In conclusion, chronic blockade of angiotensin II type 1 receptors with losartan reversed SH rats' electrical remodeling and shortened action potential duration, which was associated with an increase in Ito density as the expression levels of Kv4.2, Kv4.3 increased and the expression levels of KChIP2 decreased. However, the expression levels of Kv4.2, Kv4.3 and KChIP2 were not correlated with the change in blood pressure in the losartan treatment group. Losartan may decrease the inactivation time by increasing the expression of KChIP2.
authors.affiliation: Department of Cardiology, The General Hospital of Jinan Military Region, Jinan, Shandong 250031, P.R. China.
authors.forename: Hongming
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China.
authors.forename: Songlin
authors.initials: S
authors.lastname: Wu
authors.affiliation: Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, Hubei 430060, P.R. China.
authors.forename: Congxing
authors.initials: C
authors.lastname: Huang
authors.affiliation: Department of Cardiology, The General Hospital of Jinan Military Region, Jinan, Shandong 250031, P.R. China.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Li
mesh_terms: D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D015870:Gene Expression; D006352:Heart Ventricles / Q000187:drug effects* / Q000378:metabolism*; D006973:Hypertension / Q000188:drug therapy* / Q000235:genetics*; D007700:Kinetics; D051605:Kv Channel-Interacting Proteins / Q000235:genetics; D019808:Losartan / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism*; D015221:Potassium Channels / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D051672:Shal Potassium Channels / Q000235:genetics
chemical_list: D000959:Antihypertensive Agents; D051605:Kv Channel-Interacting Proteins; D015221:Potassium Channels; D051672:Shal Potassium Channels; D019808:Losartan