Voltage-activated Ca2+ channels in rat renal afferent and efferent myocytes: no evidence for the T-type Ca2+ current
Smirnov, S. V., Loutzenhizer, K. and Loutzenhiser, R., 2013. Voltage-activated Ca2+ channels in rat renal afferent and efferent myocytes: no evidence for the T-type Ca2+ current. Cardiovascular Research, 97 (2), pp. 293-301.
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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(2+) 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 RESULTS: Native 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 was readily demonstrated. Afferent arteriolar myocytes exhibited relatively large I(Ca) densities (-2.0 ± 0.2 pA/pF) in physiological Ca(2+) 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(2+) channels. Efferent arteriolar myocytes did not exhibit a discernible voltage-activated I(Ca) in physiological Ca(2+). CONCLUSION: Our findings support the physiological 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.
|Creators||Smirnov, S. V., Loutzenhizer, K. and Loutzenhiser, R.|
|Departments||Faculty of Science > Pharmacy & Pharmacology|
|Publisher Statement||4999_ACCEPTED_MS.pdf: This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Cardiovascular Research following peer review. The definitive publisher-authenticated version Smirnov, S. (2012). Voltage-activated Ca2+ channels in rat renal afferent and efferent myocytes: No evidence for the T-type Ca2+ current. Cardiovascular Research, 97(2), pp.293-301 is available online at: http://dx.doi.org/10.1093/cvr/cvs310|
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