Effect of rat CINC/gro, a member of the interleukin-8 family, on leukocytes in microcirculation of the rat mesentery.

Rat cytokine-induced neutrophil chemoattractant (CINC) is a member of the IL-8 family, and its human counterpart is gro/MGSA but not IL-8. We ascertained that chemically synthesized CINC was comparable to native CINC/gro with regard to chemotactic activity for rat neutrophils and studied the effect of synthesized CINC/gro on circulating leukocytes in microvascular vessels of rat mesentery. Exposure of rat mesentery to 10(-8)M authentic CINC/gro induced neutrophil adherence to and extravasation from postcapillary venules (PCVs) but not from capillaries or arterioles. CINC/gro concentrations as low as 10(-10) M were effective in causing neutrophil adherence. Neutrophils adhered to thin PCVs (mean diameter, approximately 25 microns) after exposure to CINC/gro for 15 min. The mean diameters of the PCV with adherence of neutrophils after exposure to CINC/gro for 30 and 60 min were 37 and 43 microns, respectively. The diameters of PCV with extravasation of neutrophils also increased in a time-dependent manner. The starting position of adherence of neutrophils was approximately 25-50 microns away from the upper junction of two vessels and remained virtually unchanged during exposure to CINC/gro for 60 min. However, the distance from the start to the end of neutrophil adherence increased in a time-dependent manner. The effect of CINC/gro on adherence and extravasation of leukocytes was neutrophil specific since other leukocytes such as lymphocytes and monocytes were not identified among the adherent and extravasated leukocytes.