Two Types of Pharmacologically Distinct Ca2+ Currents with Voltage-dependent Similarities in Zona Fasciculata Cells Isolated from Bovine Adrenal Gland

Two Types of Pharmacologically Distinct Ca2+ Currents with Voltage-dependent Similarities in Zona... Voltage-activated Ca2+ currents, in zona fasciculata cells isolated from calf adrenal gland, were characterized using perforated patch-clamp recording. In control solution (Ca2+: 2.5 mm) a transient inward current was followed, in 40% of the cells, by a sustained one. In 20 mm Ba2+, 61% of the cells displayed an inward current, which consisted of transient and sustained components. The other cells produced either a sustained or a transient inward current. These different patterns were dependent upon time in culture. Current-voltage relationships show that both the transient and sustained components activated, peaked and reversed at similar potentials: −40, 0 and +60 mV, respectively. The two components, fully inactivated at −10 mV, were separated by double-pulse protocols from different holding potentials where the transient component could be inactivated or reactivated. The decaying phase of the sustained component was fitted by a double exponential (time constants: 1.9 and 20 sec at +10 mV); that of the transient component was fitted by a single exponential (time constant: 19 msec at +10 mV). Steady-state activation and inactivation curves of the two components were superimposed. Their half activation and inactivation potentials were similar, about −15 and −34 mV, respectively. The sustained component was larger in Ba2+ than in Sr2+ and Ca2+. Ni2+ (20 μm) selectively blocked the transient component while Cd2+ (10 μm) selectively blocked the sustained one. (±)Bay K 8644 (0.5 μm) increased the sustained component and nitrendipine (0.5–1 μm) blocked it selectively. The sustained component was inhibited by calciseptine (1 μm). Both components were unaffected by ω-conotoxin GVIA and MVIIC (0.5 μm). These results show that two distinct populations of Ca2+ channels coexist in this cell type. Although the voltage dependence of their activation and inactivation are comparable, these two components of the inward current are similar to T- and L-type currents described in other cells. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Two Types of Pharmacologically Distinct Ca2+ Currents with Voltage-dependent Similarities in Zona Fasciculata Cells Isolated from Bovine Adrenal Gland

Loading next page...
 
/lp/springer_journal/two-types-of-pharmacologically-distinct-ca2-currents-with-voltage-r0XMFmYTIG
Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 2000 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002320001016
Publisher site
See Article on Publisher Site

Abstract

Voltage-activated Ca2+ currents, in zona fasciculata cells isolated from calf adrenal gland, were characterized using perforated patch-clamp recording. In control solution (Ca2+: 2.5 mm) a transient inward current was followed, in 40% of the cells, by a sustained one. In 20 mm Ba2+, 61% of the cells displayed an inward current, which consisted of transient and sustained components. The other cells produced either a sustained or a transient inward current. These different patterns were dependent upon time in culture. Current-voltage relationships show that both the transient and sustained components activated, peaked and reversed at similar potentials: −40, 0 and +60 mV, respectively. The two components, fully inactivated at −10 mV, were separated by double-pulse protocols from different holding potentials where the transient component could be inactivated or reactivated. The decaying phase of the sustained component was fitted by a double exponential (time constants: 1.9 and 20 sec at +10 mV); that of the transient component was fitted by a single exponential (time constant: 19 msec at +10 mV). Steady-state activation and inactivation curves of the two components were superimposed. Their half activation and inactivation potentials were similar, about −15 and −34 mV, respectively. The sustained component was larger in Ba2+ than in Sr2+ and Ca2+. Ni2+ (20 μm) selectively blocked the transient component while Cd2+ (10 μm) selectively blocked the sustained one. (±)Bay K 8644 (0.5 μm) increased the sustained component and nitrendipine (0.5–1 μm) blocked it selectively. The sustained component was inhibited by calciseptine (1 μm). Both components were unaffected by ω-conotoxin GVIA and MVIIC (0.5 μm). These results show that two distinct populations of Ca2+ channels coexist in this cell type. Although the voltage dependence of their activation and inactivation are comparable, these two components of the inward current are similar to T- and L-type currents described in other cells.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Jan 15, 2000

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off