Factors responsible for oscillations of membrane potential recorded with tight-seal-patch electrodes in mouse fibroblasts

Abstract

In giant fibroblastic L cells, penetration of a conventional microelectrode brought about marked decreases in the membrane potential and input resistance measured with a patch electrode under tight-seal whole-cell configuration, and repeated hyperpolarizations were often observed upon penetration. Therefore, the question arose whether such leakage artifact is a causal factor for generation of the membrane potential oscillation even in giant L cells. During whole-cell recordings, however, regular potential oscillations were observed in the cells that had not been impaled with a conventional microelectrode, as far as the Ca2+ buffer was not strong in the pipette solution. Oscillatory changes in the intracellular potential were detected by extracellular recordings with a tight-seal patch electrode in the cell-attached configuration. Thus, the potential oscillation occurs even in the absence of penetration-induced leakage or without rupture of the patch membrane. Withdrawal of a micropipette from one cell was often found to induce marked cell damage and elicit oscillatory hyperpolarizations in a neighboring cell with a certain time lag. The longer the distance between the injured and recorded cells, the greater was the time lag. Application of the cell lysate on the cell surface also gave rise to oscillatory hyperpolarizations. After repeated applications of the lysate, the membrane became unresponsive (desensitized), suggesting the involvement of receptors for the lysate factor. The lysates of different cell species (mouse lymphoma L5178Y cells or human epithelial Intestine 407 cells) produced similar effects. The effective component was heat stable and distinct from ATP. Lysate-induced hyperpolarizations were inhibited by deprivation of extracellular Ca2+ and by application of a Ca2+ channel blocker (nifedipine) or a K+ channel blocker (quinine) in the same manner as spontaneous oscillatory hyperpolarizations. It is concluded that the mouse fibroblast exhibits membrane potential oscillations, when the cell was activated, presumably via receptor systems, by some diffusible factors released from damaged cells.

AdipoQ Is a Novel Adipose-specific Gene Dysregulated in Obesity

“…Varying amounts of purified cDNA plasmid (pBluescript) were added directly to the transcription-translation mixture with no RNA polymerase (lane 1), T3 RNA polymerase (0. and C4 (56). However, recent evidence suggests that C1q can also regulate other functions such as cell-mediated cytotoxicity (57), phagocytosis (58), chemotaxis (59), and interleukin-1 production (60) via a receptor-mediated mechanism. A putative receptor for C1q has been isolated and characterized in several human and murine cells including macrophages, lymphocytes, and fibroblasts (61).…”

Mitogen‐induced oscillations of membrane potential and Ca2+ in human fibroblasts

“…The ability to generate recurring hyperpolarizations through Ca2' -activated K ' channels was already described in detaiI in the case of mouse fibroblasts [7,8]. Several other cases have been reported recently showing pulsatile calcium rises with associated membrane conductance changes [9-121. It is important to remember here that not all the tested cells responded to stimulation 121, the proportion of non-responsive cells being about 35%.…”

C1q-mediated chemotaxis by human neutrophils: involvement of gClqR and G-protein signalling mechanisms

“…The levels of C1q used in this study are similar to those found in various tissue sites during injury and inflammation. Previously, using cultured murine fibroblasts [31], mast cells [11], and eosinophils [12], it has been shown that human C1q can induce chemotaxis across species.…”