Association of free radicals and the tissue renin-angiotensin system: prospective effects of Rhodiola, a genus of Chinese herb, on hypoxia-induced pancreatic injury.

The renin-angiotensin system has long been recognized as crucial factor in the regulation of the systemic blood pressure and renal electrolyte homeostasis. Numerous studies have demonstrated the presence of a local renin-angiotensin system in a variety of organs. A recent study of the pancreatic renin-angiotensin system showed that chronic hypoxia significantly increased the mRNA expression for angiotensinogen II receptor subtypes AT1b and AT2. The activation of the renin-angiotensin system may play an important role in cellular pathophysiological processes. Angiotensin II enhances the formation of reactive oxygen species via the activation of xanthine oxidase or NAD(P)H oxidase. The reactive oxygen species can cause oxidative damage in the pancreas and other tissues either directly or indirectly via the formation of other radicals such as reactive nitrogen species. Rhodiola therapy may protect hypoxia-induced pancreatic injury in two ways. It prevents hypoxia-induced biological changes by increasing intracellular oxygen diffusion and efficiency of oxygen utilization. Alternatively, it reduces hypoxia-induced oxidative damage by its antioxidant activities. Additional experimental data are required to fully elucidate the mode of action of this herbal drug.