Spontaneous and chemoattractant-induced oscillations of cytosolic free @entity460 in single adherent XXXX neutrophils.

@entity1 @entity14915 @entity5038 @entity593 @entity460 @entity141
Studies with fluorescent @entity141 indicators in large populations of neutrophils in suspension reveal a stable base line followed by a rapid agonist-induced elevation of cytosolic free @entity460 , [ @entity141 ]i, concomitant with other parameters of cellular activation. To study the role of adhesion in cell activation, we monitored [ @entity141 ]i in single neutrophils adhered to albumin-coated or fibronectin-coated glass coverslips before and after stimulation with the chemotactic peptide @entity14915 ( @entity5038 ). @entity1 neutrophils loaded with 2 microM @entity593 /AM were allowed to adhere to coverslips for 15-20 min at 37 degrees C. [ @entity141 ]i was monitored with a dual excitation microfluorimeter with a time resolution of 200 ms. Statistical analysis was performed using an algorithm allowing to detect significant [ @entity141 ]i peaks. 54% of the cells showed spontaneous [ @entity141 ]i oscillations. The amplitude of these [ @entity141 ]i peaks averaged 77 +/- 10 nM above basal levels (mean value of 110 +/- 20 nM), and their mean duration was 28 +/- 5 s; periods of [ @entity141 ]i bursts could last up to 15 min. In "silent" cells exhibiting a stable [ @entity141 ]i base line without spontaneous oscillations, low concentrations of @entity5038 (10(-10)-10(-9) M) could induce sustained [ @entity141 ]i oscillations. By contrast, higher agonist concentrations (10(-6) M) induced a single [ @entity141 ]i transient followed by a stable base line. 47% of the cells showing spontaneous [ @entity141 ]i oscillations did not respond to @entity5038 . Spontaneous [ @entity141 ]i oscillations depended on the continuous presence of extracellular @entity141 . Therefore: (i) spontaneous oscillations of [ @entity141 ]i occur in neutrophils adherent to various substrata; (ii) these oscillations do not preclude and can be dissociated from the response to @entity5038 ; (iii) neutrophil functions might be controlled by [ @entity141 ]i oscillations rather than by sustained alterations of [ @entity141 ]i.
