A moderate decrease in temperature inhibits the calcium signaling mechanism(s) of the regulatory volume decrease in chick embryo cardiomyocytes

Abstract

Chick cardiomyocytes, when submitted to hyposmotic swelling, exhibit a partial regulatory volume decrease (RVD). A Ca 2+ influx by stretch-activated channels signals a taurine efflux and the RVD at 37 o C. We evaluated the cells performance at room temperature. Cardiomyocytes isolated and cultured from 11-day-old chick embryos were submitted to a hyposmotic solution (180 mOsm/kg H 2 O) at 37 o C and at room temperature (26 o C). Under these conditions we measured the changes in cell volume as well as the intracellular free Ca 2+ (using fura-2). During hyposmotic swelling, cells at 37 o C displayed a peak relative volume of 1.61 ± 0.03 and recovery to 1.22 ± 0.04 (N = 14), while cells at 26 o C presented a peak swell relative volume of 1.74 ± 0.06 and did not recover (1.59 ± 0.09, N = 9). Transient increases in intracellular Ca 2+ , which are characteristic of the normal RVD, were observed at both temperatures (29.1 ± 4.5% (N = 8) and 115.2 ± 42.8% (N = 5) increase at 37 o and 26 o C (P<0.05), respectively). A delay in the Ca 2+ transient increase was also observed when the cells were at 26 o C (109 ± 34 s compared to 38 ± 9 s at 37 o C, P<0.05). At room temperature the RVD does not occur because the calcium transient increase, which is an early event in the signaling of the RVD, is delayed. Also, free calcium is not cleared as in the 37 o C RVD. In the normal RVD the free calcium returns to baseline levels. The very high and persistent free calcium levels seen at room temperature can lead to unregulated enzyme activities and may promote irreversible injury and cell death.

Mechanically induced calcium signaling in chondrocytes in situ

“…30,44,45 Calcium signaling occurred faster and had higher amplitudes at 378C than at 218C, indicating that Ca 2þ signaling is temperature dependent, as has been found for other cell types. 34,35 This finding may have significant functional implications as cartilage is an avascular tissue known to change temperature significantly when exposed to ambient temperature changes 49,50 which, according to our results, may affect the ability of chondrocytes to respond to mechanical stimuli.…”

“…We hypothesized that Ca 2þ responses are greater in the dynamic than the relaxation phases of loading, that Ca 2þ signaling in situ occurs virtually instantaneous with load application, and that Ca 2þ responses to load become quicker and stronger with increasing temperatures. 34,35 …”

Mechanisms Sensing and Modulating Signals Arising From Cell Swelling

“…In chick cardiomyocytes volume recovery after hypotonic exposure was missing when cells were kept at room temperature. This lack of RVD was attributed to a delayed swelling-induced rise of Ca i observed in cells at room temperature, compared to myocytes kept at 37°C which exhibited normal RVD [200]. In excised membrane patches from lymphocytes the activation of Cl -channels was found to be strongly temperature dependent.…”

Roles of volume‐activated Cl− currents and regulatory volume decrease in the cell cycle and proliferation in nasopharyngeal carcinoma cells

“…Regulatory volume decrease associated with channel-and transport-mediated ion fluxes are known to be sensitive to temperature (Souza & Boyle 2001;Ernest et al 2005). Energy-dependent transporters typically show much larger temperature dependence than channel-mediated diffusion (Ernest et al 2005).…”