Characteristics of a Low Affinity Passive Ca2+ Influx Component in Rat Parotid Gland Basolateral Plasma Membrane Vesicles

Characteristics of a Low Affinity Passive Ca2+ Influx Component in Rat Parotid Gland Basolateral... We have previously reported the presence of two Ca2+ influx components with relatively high (KCa= 152 ± 79 μm) and low (KCa= 2.4 ± 0.9 mm) affinities for Ca2+ in internal Ca2+ pool-depleted rat parotid acinar cells [Chauthaiwale et al. (1996) Pfluegers Arch. 432:105–111]. We have also reported the presence of a high affinity Ca2+ influx component with KCa= 279 ± 43 μm in rat parotid gland basolateral plasma membrane vesicles (BLMV). [Lockwich, Kim & Ambudkar (1994) J. Membrane Biol. 141:289–296]. The present studies show that a low affinity Ca2+ influx component is also present in BLMV with KCa= 2.3 ± 0.41 mm (Vmax= 16.36 ± 4.11 nmoles of Ca2+/mg protein/min). Our data demonstrate that this low affinity component is similar to the low affinity Ca2+ influx component that is activated by internal Ca2+ store depletion in dispersed parotid gland acini by the following criteria: (i) similar KCa for calcium flux, (ii) similar IC50 for inhibition by Ni2+ and Zn2+; (iii) increase in KCa at high external K+, (iv) similar effects of external pH. The high affinity Ca2+ influx in cells is different from the low affinity Ca2+ influx component cells in its sensitivity to pH, KCl, Zn2+ and Ni2+. The low and high affinity Ca2+ influx components in BLMV can also be distinguished from each other based on the effects of Zn2+, Ni2+, KCl, and dicyclohexylcarbodiimide. In aggregate, these data demonstrate the presence of a low affinity passive Ca2+ influx pathway in BLMV which displays characteristics similar to the low affinity Ca2+ influx component detected in parotid acinar cells following internal Ca2+ store depletion. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

Characteristics of a Low Affinity Passive Ca2+ Influx Component in Rat Parotid Gland Basolateral Plasma Membrane Vesicles

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Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 1998 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002329900351
Publisher site
See Article on Publisher Site

Abstract

We have previously reported the presence of two Ca2+ influx components with relatively high (KCa= 152 ± 79 μm) and low (KCa= 2.4 ± 0.9 mm) affinities for Ca2+ in internal Ca2+ pool-depleted rat parotid acinar cells [Chauthaiwale et al. (1996) Pfluegers Arch. 432:105–111]. We have also reported the presence of a high affinity Ca2+ influx component with KCa= 279 ± 43 μm in rat parotid gland basolateral plasma membrane vesicles (BLMV). [Lockwich, Kim & Ambudkar (1994) J. Membrane Biol. 141:289–296]. The present studies show that a low affinity Ca2+ influx component is also present in BLMV with KCa= 2.3 ± 0.41 mm (Vmax= 16.36 ± 4.11 nmoles of Ca2+/mg protein/min). Our data demonstrate that this low affinity component is similar to the low affinity Ca2+ influx component that is activated by internal Ca2+ store depletion in dispersed parotid gland acini by the following criteria: (i) similar KCa for calcium flux, (ii) similar IC50 for inhibition by Ni2+ and Zn2+; (iii) increase in KCa at high external K+, (iv) similar effects of external pH. The high affinity Ca2+ influx in cells is different from the low affinity Ca2+ influx component cells in its sensitivity to pH, KCl, Zn2+ and Ni2+. The low and high affinity Ca2+ influx components in BLMV can also be distinguished from each other based on the effects of Zn2+, Ni2+, KCl, and dicyclohexylcarbodiimide. In aggregate, these data demonstrate the presence of a low affinity passive Ca2+ influx pathway in BLMV which displays characteristics similar to the low affinity Ca2+ influx component detected in parotid acinar cells following internal Ca2+ store depletion.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Mar 15, 1998

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