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Electrophysiological and molecular characterization of the inward rectifier in juxtaglomerular cells from rat kidney
Author(s) -
Leichtle Anke,
Rauch Ulrich,
Albinus Margitta,
Benöhr Peter,
Kalbacher Hubert,
Mack Andreas F.,
Veh Rüdiger W.,
Quast Ulrich,
Russ Ulrich
Publication year - 2004
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2004.070359
Subject(s) - afferent arterioles , juxtaglomerular apparatus , electrophysiology , macula densa , arteriole , renin–angiotensin system , patch clamp , kidney , nephron , chemistry , membrane potential , medicine , endocrinology , biophysics , anatomy , microbiology and biotechnology , biology , neuroscience , circulatory system , blood pressure
Renin, the key element of the renin–angiotensin–aldosterone system, is mainly produced by and stored in the juxtaglomerular cells in the kidney. These cells are situated in the media of the afferent arteriole close to the vessel pole and can transform into smooth muscle cells and vice versa. In this study, the electrophysiological properties and the molecular identity of the K + channels responsible for the resting membrane potential (∼−60 mV) of the juxtaglomerular cells were examined. In order to increase the number of juxtaglomerular cells, afferent arterioles from NaCl‐depleted rats were used, and > 90% of the afferent arterioles were renin positive at the distal end of the arteriole. Whole‐cell and cell‐attached single‐channel patch‐clamp experiments showed that juxtaglomerular cells are endowed with a strongly inwardly rectifying K + channel (Kir). The channel was highly sensitive to inhibition by Ba 2+ (inhibition constant 37 μ m at 0 mV), but relatively insensitive to Cs + and, with 142 m m K + in the pipette, had a single‐channel conductance of 31.5 pS. Immunocytochemical studies showed the presence of Kir2.1 but no signal for Kir2.2 in the media of the afferent arteriole. In PCR analyses using isolated juxtaglomerular cells, the mRNA for Kir2.1 and Kir2.2 was detected. Collectively, the results show that Kir2.1 is the dominant component of the channel. The current carried by these channels plays a decisive role in setting the membrane potential of juxtaglomerular cells.