We investigated whether alterations in the mechanisms involved in intracellular pH (pH(in)) and intracellular calcium ([Ca2+](in)) homeostasis are associated with the metastatic potential of poorly (A375P) and highly (C8161) metastatic human melanoma cells. We monitored pH(in) and [Ca2+](in) simultaneously, using the fluorescence of SNARF-1 and Fura-2, respectively. Our results indicated that steady-state pH(in) and [Ca2+](in) between these cell types were not significantly different. Treatment of cells with NH4Cl resulted in larger pH(in) increases in highly than in poorly metastatic cells, suggesting that C8161 cells have a lower H+ buffering capacity than A375P. NH4Cl treatment also increased [Ca2+](in) only in C8161 cells. To determine if the changes in [Ca2+](in) triggered by NH4Cl treatment were due to alterations in either H+- or Ca2+-buffering capacity, cells were treated with the Ca2+-ionophore 4Br-A23187, to alter [Ca2+](in). The magnitude of the ionophore-induced [Ca2+](in) increase was slightly greater in C8161 cells than in A375P. Moreover, A375P cells recover from the ionophore-induced [Ca2+](in) load, whereas C8161 cells did not, suggesting that A375P may exhibit distinct ICa2+](in) regulatory mechanisms than C8161 cells, to recover from Ca2+ loads. Removal of extracellular Ca2+ ([Ca2+](in)) decreased [Ca2+](in) in both cell types at the same extent. Ionophore treatment in the absence of [Ca2+](ex) transiently increased [Ca2+](in) in C8161, but not in A375P cells. Endoplasmic reticulum (ER) Ca2+-ATPase inhibitors such as cyclopiazonic acid (CPA) and thapsigargin (TG) increased steady-state [Ca2+](in) only in C8161 cells. Together, these data suggest that the contribution of intracellular Ca2+ stores for [Ca2+](in) homeostasis is greater in highly than in poorly metastatic cells. Bafilomycin treatment, to inhibit V-type H+-ATPases, corroborated our previous results that V-H+-ATPases are functionally expressed at the plasma membranes of highly metastatic, but not in poorly metastatic cells (Martinez-Zaguilan et al., 1993). Collectively, these data suggest that distinct pH(in) and [Ca2+](in) regulatory mechanisms are present in poorly and highly metastatic human melanoma cells.
|Original language||English (US)|
|Number of pages||10|
|Journal||Journal of Cellular Physiology|
|State||Published - Jul 1998|
ASJC Scopus subject areas
- Clinical Biochemistry
- Cell Biology