PMID- 2826501 OWN - NLM STAT- MEDLINE DCOM- 19880223 LR - 20131121 IS - 0021-9541 (Print) IS - 0021-9541 (Linking) VI - 134 IP - 1 DP - 1988 Jan TI - Time dependence of transmembrane potential changes and intracellular calcium flux in stimulated human monocytes. PG - 131-6 AB - An important characteristic of the functional differentiation of the blood monocyte is the development of its capacity to recognize and respond to stimuli. This ability is mediated to a large extent by specific receptor glycoproteins located on the cell surface. Stimulation of mononuclear phagocytes via these receptors results in a rapid rise in intracellular Ca++ concentration, accompanied or followed by a change in membrane potential, generation of oxidative products, degranulation, and effector functions such as phagocytosis, aggregation, or locomotion. While the development of these characteristics is difficult to characterize in vivo, several investigators have demonstrated in vitro changes in these cells that correlate with the development of effector function. To examine the mechanisms of specific membrane-stimulus interactions of monocytes as they differentiate into macrophage-like cells, we studied the responses of human monocytes and of monocytes incubated in serum-containing medium for up to 96 hr to the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (fMLP). Freshly isolated monocytes exhibited little change in transmembrane potential following stimulation with an optimal concentration of peptide and underwent a significant increase only after 48 hr in culture. While constant resting intracellular Ca++ concentrations were maintained during the culture period, intracellular Ca++ levels following fMLP stimulation increased with with incubation in serum, for up to 96 hr. In contrast, fMLP-induced respiratory burst activity increased from 0 to 24 hr in culture; it remained elevated at 48 hr but declined again by 96 hr. Incubation of the cells for 24 hr increased their random (unstimulated) motility in modified Boyden chambers but did not alter the cells' directed (chemotactic) response to fMLP in comparison to the response of freshly isolated monocytes. Peptide binding to the cells did not increase during the incubation period, indicating that an increase in receptor number or in affinity for fMLP was not responsible for the enhanced responsiveness to fMLP as incubation time increased. These studies indicate that incubation of monocytes in serum-containing medium leads to a complex, altered series of responses to fMLP that correlate with the differentiation of the original monocytes in vitro and may relate to the in vivo differentiation of monocytes to macrophages. FAU - Bernardo, J AU - Bernardo J AD - Department of Medicine, Boston University School of Medicine, Massachusetts 02118. FAU - Brink, H F AU - Brink HF FAU - Simons, E R AU - Simons ER LA - eng GR - AM-31056/AM/NIADDK NIH HHS/United States GR - HL-19717/HL/NHLBI NIH HHS/United States GR - HL-33565/HL/NHLBI NIH HHS/United States PT - Journal Article PT - Research Support, U.S. Gov't, P.H.S. PL - United States TA - J Cell Physiol JT - Journal of cellular physiology JID - 0050222 RN - 0 (Cytochrome c Group) RN - 11062-77-4 (Superoxides) RN - 59880-97-6 (N-Formylmethionine Leucyl-Phenylalanine) RN - SY7Q814VUP (Calcium) SB - IM MH - Calcium/*metabolism MH - Chemotaxis, Leukocyte MH - Cytochrome c Group/metabolism MH - Electrophysiology MH - Humans MH - Intracellular Membranes/*metabolism MH - Monocytes/metabolism/*physiology MH - N-Formylmethionine Leucyl-Phenylalanine/pharmacology MH - Oxidation-Reduction MH - Stimulation, Chemical MH - Superoxides/biosynthesis MH - Time Factors EDAT- 1988/01/01 00:00 MHDA- 1988/01/01 00:01 CRDT- 1988/01/01 00:00 PHST- 1988/01/01 00:00 [pubmed] PHST- 1988/01/01 00:01 [medline] PHST- 1988/01/01 00:00 [entrez] AID - 10.1002/jcp.1041340116 [doi] PST - ppublish SO - J Cell Physiol. 1988 Jan;134(1):131-6. doi: 10.1002/jcp.1041340116.