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Voltage-Activated Ca2+ Channels in Rat Renal Afferent and Efferent Myocytes: No Evidence for the T-Type Ca2+ Current.
MedLine Citation:
PMID:  23042470     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
AIMS: Based on indirect methods, it has been suggested that both L- and T-type Ca(2+) channels mediate signalling in the renal afferent arteriole and that T-type Ca channels are involved in signalling in the efferent arteriole. However, Ca(2+) currents have never been studied in these two vessels. Our study was initiated to directly determine the type of Ca(2+) channels in these vessels for the first time, using patch clamp.Methods and ResultsNative myocytes were obtained from individually isolated rat renal afferent and efferent arterioles and from rat tail arteries (TA). TA myocytes, which possess both L- and T-type Ca(2+) currents, served as a positive control. Inward Ca(2+) and Ba(2+) currents (I(Ca) and I(Ba)) were measured in 1.5 mmol/L Ca(2+) and 10 mmol/L Ba(2+), respectively, using the whole-cell configuration. By exploiting known differences in activation and inactivation characteristics and differing sensitivities to nifedipine and kurtoxin, the presence of both L- and T-type Ca(2+) channels in TA myocytes were readily demonstrated. Afferent arteriolar myocytes exhibited relatively large I(Ca) densities (-2.0±0.2 pA/pF) in physiologic Ca and the I(Ba) was 3.6 fold greater. These currents were blocked by nifedipine, but not by kurtoxin and did not exhibit the activation and inactivation characteristics of T-type Ca channels. Efferent arteriolar myocytes did not exhibit a discernable voltage-activated I(Ca)in physiologic Ca(2+). CONCLUSIONS: Our findings support the physiologic role of L-type Ca(2+) channels in the afferent, but not efferent, arteriole, but do not support the premise that functional T-type Ca(2+) channels are present in either vessel.
Authors:
Sergey Smirnov; Kathy Loutzenhiser; Rodger Loutzenhiser
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-4
Journal Detail:
Title:  Cardiovascular research     Volume:  -     ISSN:  1755-3245     ISO Abbreviation:  Cardiovasc. Res.     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-8     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0077427     Medline TA:  Cardiovasc Res     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, BA2 7AY, England.
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