In vitro activation of neutrophils of the aged by recombinant human growth hormone

Several functions of polymorphonuclear neutrophils (PMNL) have been found to be altered in the aged. As the neuroendocrine network, in particular growth hormone (GH), may interfere with the regulation of nonspecific host defense mechanisms, a recently described PMNL-priming activity of recombinant human (rH) GH in vitro was investigated. Oxidative metabolism of PMNL from young and old subjects was studied by measuring reduction of nitroblue tetrazolium (NBT) or cytochrome c. In the absence of stimulating agents, PMNL from old subjects reduced NBT to a significantly lesser extent than did PMNL from young subjects. Addition of rHGH to PMNL from old subjects reversed the suppressed spontaneous oxidative metabolism. No differences between young and old were observed for the increase of stimulated oxidative metabolism. The results suggest that altered PMNL function in the aged may be reversed by rHGH and that the ability of PMNL to respond to rHGH does not decline with age.