Marked alterations in circulating inflammatory cells during cardiomyopathy development in a magnesium-deficient rat model

Rodents fed on a Mg-deficient (Mg-D) diet develop cardiomyopathic lesions, as well as other types of cardiovascular dysfunction. In the rat, inflammatory cell infiltration of the myocardium begins to occur by week 1, and the lesions develop extensively in the third and fourth weeks on the Mg-D diet. Although the aetiologic mechanisms of Mg-D cardiomyopathy are unknown, we have previously reported that once plasma Mg is markedly reduced, one of the earliest molecular markers of the pathophysiological process is elevation of plasma substance P, calcitonin gene-related peptide and prostaglandin E2, followed by histamine and the inflammatory cytokines (interleukin-1, interleukin-6, and tumor necrosis factor-alpha). In order to evaluate the potential role of specific circulating inflammatory cell subpopulations in the mechanisms underlying pathophysiological changes observed in Mg-deficiency-induced cardiomyopathy, we analysed these cells by flow cytochemistry. Leucocyte subpopulation pools increased progressively in the Mg-D rats. Elevated circulating levels of neutrophils and lymphocytes appeared to contribute to both the acute (week 1-2) and chronic phases (week 3-4) of the inflammatory responses; monocytes, eosinophils, basophils and large unstained cells which are lymphoid in stained smears, on the other hand, increased significantly in the third and fourth weeks and thus contributed to the chronic inflammatory phase. Changes in the circulating leucocyte subpopulations paralleled the chronological progression of the cardiomyopathic lesions, particularly in weeks 3 and 4. Since a pronounced neutrophilia preceded leucocyte infiltration and deposition within the myocardial tissue, modifications of the microvascular barrier may be a prerequisite for cardiomyopathy in this model of neurogenic inflammation.