Leukocyte inhibitory factor (LIF) potentiates neutrophil responses to formyl-methionyl-leucyl-phenylalanine

The ability of purified (80,000-fold) human leukocyte inhibitory factor (LIF) to modulate several formyl-methionyl-leucyl-phenylalanine (f-met-leu-phe)-induced neutrophil functions was evaluated. Although not affecting directed migration itself, at low concentrations (1/2 to 2 U/ml), LIF was demonstrated to potentiate chemotaxis induced by f-met-leu-phe (40.3% +/- 8.1) and to reduce the concentration of f-met-leu-phe necessary for maximal chemotaxis (10(-8) to 10(-9) M). Similarly, LIF did not directly induce the respiratory burst, but potentiated both superoxide generation (151.6% +/- 77) and hydrogen peroxide production (54.9% +/- 15.5) in the presence of f-met-leu-phe (10(-7) M). LIF was also shown to induce degranulation of neutrophil-specific granules in a dose-dependent manner. Neutrophil-specific granules have been shown to contain an intracellular pool of receptors for f-met-leu-phe, and on degranulation provide the surface membrane with a fresh source of receptors. Our data suggested that LIF potentiation of neutrophil stimulation by f-met-leu-phe might be mediated, at least in part, by increasing the number of available membrane receptors as a result of its ability to induce degranulation. Radioligand receptor analysis using f-met-leu-[3H] phe was performed, and LIF was shown to mediate an increase in receptors for f-met-leu-phe from an average of 18,600 on untreated cells to 27,000 after pretreatment with LIF. This increase in receptors could "sensitize" the neutrophils for f-met-leu-phe and possibly explain the potentiation of neutrophil stimulation observed in the presence of the ligand. LIF was also found to have a more generalized effect on the transduction of neutrophil activation stimuli, mediating a 35.8% increase in superoxide production after exposure to calcium ionophore. The data do not permit a determination as to whether the increase in receptor number is responsible for the potentiation of f-met-leu-phe-mediated function, or whether this occurs secondary to the more generalized effect on neutrophil stimulation transduction.

Leukocyte inhibitory factor (LIF) potentiates neutrophil responses to formyl-methionyl-leucyl-phenylalanine

The ability of purified (80,000-fold) human leukocyte inhibitory factor (LIF) to modulate several formyl-methionyl-leucyl-phenylalanine (f-met-leu-phe)-induced neutrophil functions was evaluated. Although not affecting directed migration itself, at low concentrations (1/2 to 2 U/ml), LIF was demonstrated to potentiate chemotaxis induced by f-met-leu-phe (40.3% +/- 8.1) and to reduce the concentration of f-met-leu-phe necessary for maximal chemotaxis (10(-8) to 10(-9) M). Similarly, LIF did not directly induce the respiratory burst, but potentiated both superoxide generation (151.6% +/- 77) and hydrogen peroxide production (54.9% +/- 15.5) in the presence of f-met-leu-phe (10(-7) M). LIF was also shown to induce degranulation of neutrophil-specific granules in a dose-dependent manner. Neutrophil-specific granules have been shown to contain an intracellular pool of receptors for f-met-leu-phe, and on degranulation provide the surface membrane with a fresh source of receptors. Our data suggested that LIF potentiation of neutrophil stimulation by f-met-leu-phe might be mediated, at least in part, by increasing the number of available membrane receptors as a result of its ability to induce degranulation. Radioligand receptor analysis using f-met-leu-[3H] phe was performed, and LIF was shown to mediate an increase in receptors for f-met-leu-phe from an average of 18,600 on untreated cells to 27,000 after pretreatment with LIF. This increase in receptors could "sensitize" the neutrophils for f-met-leu-phe and possibly explain the potentiation of neutrophil stimulation observed in the presence of the ligand. LIF was also found to have a more generalized effect on the transduction of neutrophil activation stimuli, mediating a 35.8% increase in superoxide production after exposure to calcium ionophore. The data do not permit a determination as to whether the increase in receptor number is responsible for the potentiation of f-met-leu-phe-mediated function, or whether this occurs secondary to the more generalized effect on neutrophil stimulation transduction.

Prediction of steady-state trough serum procainamide concentrations after administration of a sustained-release procainamide preparation

Four methods of predicting steady-state trough serum procainamide concentrations (SPC) were compared in 15 patients receiving sustained-release procainamide (Procan-SR) therapy. All methods were based on a one-compartment pharmacokinetic model. Method 1 utilized nine initial measured SPC and individualized pharmacokinetic parameters for prediction of the steady-state SPC. Method 2 utilized three SPC and individualized pharmacokinetic parameters. Method 3 utilized two SPC and an individualized apparent elimination rate constant plus other average pharmacokinetic parameters. Method 4 utilized all averaged pharmacokinetic parameters (required no initial SPC). The predicted and measured SPCs for each method were analyzed by linear regression. Regression equations and correlation coefficients (r) for Methods 1, 2, 3, and 4 were as follows: predicted SPC = 0.72 measured SPC + 1.60 (r = 0.86), predicted SPC = 0.67 measured SPC + 1.74 (r = 0.82), predicted SPC = 0.13 measured SPC + 2.57 (r = 0.58), and predicted SPC = 0.15 measured SPC + 2.47 (r = 0.52), respectively. The precision, as measured by the mean squared prediction error (95% confidence interval) for Methods 1, 2, 3, and 4 was 1.44 (0.61, 2.27), 1.75 (0.93, 2.57), 2.81 (1.3, 4.49), and 3.68 (1.12, 6.26), respectively. (Eighty-five percent of the predictions were within +/- 1.5 micrograms/ml of the measured SPC by Methods 1 and 2, as compared with 69% by Methods 3 and 4.) Bias, as measured by the mean prediction error (95% confidence interval) for Methods 1, 2, 3, and 4 were -0.44 (-0.90, 0.03), -0.34 (-0.87, 0.18), -0.43 (-1.09, 0.24), and -0.98 (-1.66, -0.31).(ABSTRACT TRUNCATED AT 250 WORDS)