Hypomagnesemia is the most concerned side effect of proton pump inhibitors (PPIs) in chronic users. However, the mechanism of PPIs-induced systemic Mg2+ deficit is currently unclear. The present study aimed to elucidate the direct effect of short-term and long-term PPIs administrations on whole body Mg2+ homeostasis and duodenal Mg2+ absorption in rats. Mg2+ homeostasis was studied by determining the serum Mg2+ level, urine and fecal Mg2+ excretions, and bone and muscle Mg2+ contents. Duodenal Mg2+ absorption as well as paracellular charge selectivity were studied. Our result showed that gastric and duodenal pH markedly increased in omeprazole-treated rats. Omeprazole significantly suppressed plasma Mg2+ level, urinary Mg2+ excretion, and bone and muscle Mg2+ content. Thus, omeprazole induced systemic Mg2+ deficiency. By using Ussing chamber techniques, it was shown that omeprazole markedly suppressed duodenal Mg2+ channel-driven and Mg2+ channel-independent Mg2+ absorptions and cation selectivity. Inhibitors of mucosal HCO3- secretion significantly increased duodenal Mg2+ absorption in omeprazole-treated rats. We therefore hypothesized that secreted HCO3- in duodenum decreased luminal proton, this impeded duodenal Mg2+ absorption. Higher plasma total 25-OH vitamin D, diuresis, and urine PO43- were also demonstrated in hypomagnesemic rats. As a compensatory mechanism for systemic Mg2+ deficiency, the expressions of duodenal transient receptor potential melastatin 6 (TRPM6), cyclin M4 (CNNM4), claudin (Cldn)-2, Cldn-7, Cldn-12, and Cldn-15 proteins were enhanced in omeprazole-treated rats. Our findings support the potential role of duodenum on the regulation of Mg2+ homeostasis.
Keywords: Hypomagnesemia; Intestinal Mg2+absorption; Mg2+ homeostasis; Proton pump inhibitors; Ussing chamber.