EFFECTS OF GROWTH-HORMONE AND INSULIN-LIKE-GROWTH-FACTOR-I ON OPSONINRECEPTOR EXPRESSION ON LOCAL AND SYSTEMIC PHAGOCYTES IN A LETHAL PERITONITIS MODEL

Objective: To investigate the effects of pretreatment with growth horm one (GH) and insulin like growth factor I (IGF-I) on phagocyte exudati on and bacterial clearance, focusing on CD11b and CD32/CD16 expression on local and systemic phagocytes, in a lethal peritonitis model. Desi gn: Prospective randomized experimental study. Setting: Research labor atory in a university hospital. Subjects: Balb/c mice (n = 21). Interv entions: Mice were challenged intraperitoneally with 1 x 10(8) Escheri chia coli, after 6 days of pretreatment with saline (control), GH (4.8 mg/kg/day), or IGF-I (24 mg/kg/day). Samples were harvested at 4 hrs after the challenge. Measurements and Main Results: Viable bacterial c ounts in peritoneal lavage fluid (PLF) and blood were determined. Peri toneal exudative cells and peripheral blood leukocytes were counted an d analyzed for receptor expressions by flow cytometry. GH reduced viab le bacterial counts in PLF, as compared with the saline control. GH (t hree fold) and IGF I (two fold) increased the number of peritoneal exu dative neutrophils (PENs), as compared with the saline control. The nu mber of PENs showed an inverse correlation with PLF viable bacterial c ounts. By contrast, there were no differences in peripheral blood neut rophil (PN) counts among the three groups, nor was there a correlation between PN and PEN counts. CD11b expression was greater on PENs than on PNs in all three groups. CD11b expression on PNs did not differ amo ng the three groups. However, GH increased CD11b expression on PENs, a s compared with saline and IGF-I, and this expression showed a positiv e correlation with PEN numbers and an inverse correlation with PLF via ble bacterial counts. CD11b expression on peritoneal macrophages and p eripheral blood monocytes did not differ among the three groups. There were no differences in phagocyte CD32/CD16 expression among the three groups. Conclusions: GH pretreatment enhanced CD11b expression on PEN s, but not PNs, possibly in association with enhanced neutrophil recru itment, phagocytosis, and bacterial elimination by PENs, without activ ation of PNs. GH prophylaxis may be useful for reducing the frequency rate and severity of septic complications, via modulation of CD11b exp ression on local and systemic neutrophils.