title: Increased oxygen consumption observed in phorbol 12-myristate 13-acetate stimulated human cultured promonocytic U937 cell lines treated with calcitriol and retinoic acid.
abstract: OBJECTIVE
  To investigate the effect of phorbol 12-myristate 13-acetate (PMA) and formyl-methionyl-leucyl-phenylalanine (FMLP) on oxygen consumption of differentiated and non-differentiated immune cell lines by retinoic acid and calcitriol treatment which might be useful in subsequent elicitation of immunological action during immunosuppressive states.
  
  
  METHODS
  PMA and FMLP were used to artificially stimulate reactive oxygen production in cultured promonocytic U937 cell line. Paralleled samples of the cultured cells were separately prepared with calcitriol (1, 25- dihydroxyvitamin D3) and retinoic acid followed by a 72-hour incubation period. The rate of respiratory burst was measured using the Clark oxygen electrode.
  
  
  RESULTS
  The average increase in cell concentrations per mL observed was significantly higher in retinoic acid-treated cells (9×10(6) cells/mL) when compared with calcitriol-treated samples (4×10(6) cells/mL). There was a marked increase in oxygen consumption of the calcitriol-treated cell lines against the retinoic acid-treated ones. Exposure of differentiated U937 cells to PMA and FMLP increased significantly (P<0.05) in their oxygen consumption when compared with the control. PMA calcitriol-treated cells resulted in 55% oxygen consumption more than the control while FMLP oxygen consumption increased 78% by comparison with the control.
  
  
  CONCLUSIONS
  The result demonstrated that calcitriol may serve as a physiological promoter of normal differentiation of precursor cells which may exert an immunological action. This effect could elicit a marker potential and increase immune cell activity of the host especially in immunosuppressed diseased states.
authors.affiliation: School of Health, Sport and Bioscience, University of East London, United Kingdom.
authors.forename: Samson Ayodeji
authors.initials: SA
authors.lastname: Olofinsae
authors.affiliation: Departments of Medical Biotechnology, National Biotechnology Development Agency, Abuja, Nigeria. Electronic address: barthokeyibeh@yahoo.com.
authors.forename: Bartholomew Okechukwu
authors.initials: BO
authors.lastname: Ibeh
authors.affiliation: School of Health, Sport and Bioscience, University of East London, United Kingdom.
authors.forename: Jatinder
authors.initials: J
authors.lastname: Ahluwalia
keywords: Calcitriol; Immunity; NADPH oxidase; Oxidation; Promonocytes; Respiratory burst; Retinoic acid; U937 cell lines