Agonistic activities of histamine-albumin conjugates at histamine H2 receptors on human HL-60 promyelocytic leukemia cells.
We previously identified functional histamine H2 receptors on human HL-60 promyelocytic leukemia cells [J. Biol. Chem. 264: 18356-18362 (1989)]. In the present study, we have compared the action of histamine-albumin conjugates on H2 receptor activation with that of histamine alone. Both histamine and conjugates increased intracellular levels of Ca2+ in an H2 receptor-specific manner. However, binding of fluoresceinated histamine-albumin conjugates to HL-60 cells was not dissociated by 10(-4) M unlabeled histamine, although this concentration of histamine significantly desensitized conjugate responses. These data suggest that histamine-albumin conjugates not only activate H2 receptors but also bind to HL-60 cells nonspecifically or in an H2 receptor-unrelated manner. Moreover, histamine-induced Ca2+ mobilization was transient, whereas conjugate-induced Ca2+ mobilization was sustained for more than 10 min, as a result of the influx of extracellular Ca2+. Therefore, the functional difference between histamine and conjugates may provide a good model for the further understanding of the activation mechanisms of receptor-operated Ca2+ influx.
Mitsuhashi
M
M
Howard Hughes Medical Institute Laboratory, San Francisco, California.
Mitsuhashi
T
T
Dazin
P F
PF
Payan
D G
DG
D000418:Albumins / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D005434:Flow Cytometry; D006632:Histamine / Q000494:pharmacology*; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000378:metabolism / Q000473:pathology; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D011970:Receptors, Histamine H2 / Q000187:drug effects*; D014407:Tumor Cells, Cultured
D000418:Albumins; D011970:Receptors, Histamine H2; D009240:N-Formylmethionine Leucyl-Phenylalanine; D006632:Histamine; D002118:Calcium