Missing link in anaemia: arginine vasopressin
A brain hormone that controls water balance in the body also plays a key role in creating new blood cells, a new study has shown.
Anti-diuretic hormone, also called AVP or arginine vasopressin, is released into the circulation by the brain's pituitary gland to control water reabsorption by the kidney.
If we become dehydrated, or suffer blood loss, a surge of AVP puts the kidney into a water conserving state, and it triggers blood vessels to constrict to help us to maintain blood pressure.
Now scientists have stumbled on an additional, previously overlooked action of AVP, which could make an important clinical contribution: it also triggers the bone marrow to produce new blood cells.
Writing in Science Translational Medicine, NIH researcher Balázs Mayer and his colleagues noticed that up to 87% of patients with a condition preventing them from making AVP were anaemic; that is, they had too few red blood cells.
The team carried out tests on human, rat and mouse bone marrow stem cells and showed that incubating the cells with AVP rapidly increases the rates of cell growth and the production of red blood cell precursors.
The stem cells, they found, express receptors on their surfaces that recognise and respond to AVP, triggering them to grow. Indeed, bone marrow cells exposed to AVP in a culture dish proliferated 50% more over a 12 day period compared with control samples.
The NIH team also found that giving AVP to animals that had lost blood resulted in a significant and rapid increase in replacement red blood cells.
Currently, the hormone erythropoietin, which is made by the kidney and also acts on the bone marrow, is widely used in patients prone to anaemia. But this takes up to 5 days to achieve its effect and is used by the body to achieve a long-term steady control over blood cell counts. AVP, on the other hand, works much more rapidly.
This, say the researchers, means that it may have considerable therapeutic potential to help patients suffering from a range of disorders including bleeding, the side effects of chemotherapy, or the toxic impacts of drugs or radiation treatments.
The observation also settles a mystery from many decades ago when scientists showed that, following a haemorrhage, rats produce two surges of blood production in their bone marrow - one after just 4 hours and another beginning 18 hours later. The first surge, these scientists had noted, disappears in rats without a pituitary gland although they could not explain why. Now we know...