The role of sarcolemmal Ca²⁺‐ATPase in the regulation of resting calcium concentration in rat ventricular myocytes

Abstract

The aim of this work was to investigate the role of sarcolemmal Ca2+‐ATPase in rat ventricular myocytes. We have measured intracellular Ca2+ concentration ([Ca2+]i) using indo‐1. The actions of the ATPase inhibitor carboxyeosin were studied. Carboxyeosin increased resting [Ca2+]i and the magnitude of the systolic Ca2+ transient and slowed the rate of its relaxation by 5%. Carboxyeosin increased the magnitude of the caffeine‐evoked increase in [Ca2+]i and slowed its relaxation by 20%. Removal of extracellular Na+ slowed the rate constant by 80%. When Na+ was removed in a carboxyeosin‐treated cell, the caffeine‐evoked increase in [Ca2+]i did not decay. Carboxyeosin increased the integral of the Na+‐Ca2+ exchange current activated by caffeine. This is, in part, due to an increase in sarcoplasmic reticulum Ca2+ content. When extracellular Na+ was removed, there was a transient increase in [Ca2+]i which then decayed. The rate of this decay was slowed by carboxyeosin by a factor of about four. The residual decay could be abolished with caffeine. In the absence of extracellular Na+, increasing extracellular Ca2+ concentration ([Ca2+]o) elevated [Ca2+]i. In carboxyeosin‐treated cells, [Ca2+]i was much more sensitive to [Ca2+]o. These results demonstrate the role of a carboxyeosin‐sensitive Ca2+‐ATPase in the control of resting [Ca2+]i and the reduction in [Ca2+]i following an increase in [Ca2+]i.

Interaction of the Plasma Membrane Ca2+ Pump 4b/CI with the Ca2+/Calmodulin-dependent Membrane-associated Kinase CASK

“…These results provide evidence of a new direct Ca 2؉ -dependent link from the plasma membrane to the nucleus. (12). In contrast to these observations, overexpression of PMCA4b in the myocardium of transgenic rats did not result in an altered regulation of contraction/relaxation cycle but in an enhanced growth response of cardiac myocytes to different stimuli (13).…”

“…Recently, a role of the carboxyeosin-sensitive Ca 2ϩ -ATPase PMCA in controlling resting [Ca 2ϩ ] i and the reduction in [Ca 2ϩ ] i after an increase in [Ca 2ϩ ] i in rat ventricular myocytes has been demonstrated (12). In contrast to these observations, overexpression of PMCA4b in the myocardium of transgenic rats did not result in an altered regulation of contraction/relaxation cycle but in an enhanced growth response of cardiac myocytes to different stimuli (13).…”

Calcium in ciliated protozoa: Sources, regulation, and calcium-regulated cell functions

“…As a rule, we see no activation of exocytosis in parallel to a ciliary reversal reaction, whereas the opposite effect does occur (Section III.D). In cardiac myocytes, for example, the Na+/Ca 2 +exchanger is approximately four times more effective than the plasmalemmal Ca 2 + pump (Choi and Eisner, 1999).…”

Development and characterization of a novel fluorescent indicator protein PMCA4-GCaMP2 in cardiomyocytes

“…Inhibitors used in previous studies have either been general inhibitors of the ATPase family such as lanthanum, vanadate and eosin [31][32][33][34][35][36][37], or general calmodulin antagonists such as calmidazolium [38]. Currently, carboxyeosin is the only available non-specific pharmacological inhibitor for PMCA [39]. However, carboxyeosin is a fluorescent compound and would interfere with the GCaMP2 signal.…”