<p>The naked mole-rat (<i>Heterocephalus glaber</i>) is a long-lived rodent renowned for its remarkable resistance to cancer and age-related diseases. Its immune system has a unique cellular composition with a predominance of myeloid cells. Previously, we reported that naked mole-rat macrophages activated in vitro with lipopolysaccharide (LPS) and interferon-gamma produce significantly less nitric oxide (NO) compared to laboratory mouse (<i>Mus musculus</i>) macrophages. Furthermore, genes involved in arginine metabolism show distinct expression patterns between the two species following pro-inflammatory macrophage activation. To address the inflammation-induced species-specific profile of NO metabolism in vivo, a model of acute LPS-induced systemic inflammation was used. 24&#xa0;h after LPS administration blood cell composition, intracellular NO production, expression of arginine metabolism-related genes and cytokines were analyzed in whole tissues as well as in sorted splenic CD11b⁺ cells. LPS administration induced sickness behavior and increased inflammatory cytokine gene expression in the spleen and the liver of both naked mole-rats and mice. However, naked mole-rats exhibited a species-specific reduction in inducible NO-synthase (iNOS) activity: the intracellular NO levels were significantly elevated in myeloid blood cells after LPS administration in mice, but not in naked mole-rats. The expression of the gene coding for iNOS, <i>Nos2,</i> was upregulated in a dose-dependent manner in murine tissues, whereas in naked-mole rats, <i>Nos2</i> induction was observed only after high-dose LPS administration in the liver. Additionally, an alternative arginine-utilizing pathway involved in creatine synthesis remained unaffected by LPS administration in naked mole-rat tissues, in contrast to mice. These findings suggest that naked mole-rats may tolerate acute inflammation due to metabolic adaptations that modulate iNOS activation in myeloid cells.</p>