Renomedullary Blood Flow And Blood Volume Are Increased During Vasopressin Escape
2010 (English)Conference paper (Refereed)
Hyponatremia is a common electrolyte disorder usually caused by inappropriate vasopressin (AVP) levels relative to serum osmolality. The degree of the hyponatremia is limited by "escape" from AVP-induced antidiuresis, characterized by increased urine volume and decreased urine osmolality independently of circulating AVP. The mechanisms mediating escape are not fully understood, but we have hypothesized that increased renomedullary blood flow (BF) contributes to this process. We therefore investigated intrarenal BF and blood volume distribution in rats with and without escape.
Adult male Sprague-Dawley rats (n=10) were infused with DDAVP (5 ng/h) to produce maximal antidiuresis. Half were fed a liquid diet (AIN-76) to produce escape; half were fed a solid diet to prevent escape. After 5 days, all rats were anesthetized with Inactin and high resolution images (voxel size 97x97x600 µm) of renal BF were acquired using a Siemens Definition Dual Source CT. Iopromide (0.15 ml/rat) was rapidly injected iv and the contrast over the kidney area was collected during 30 s. Data were evaluated by analyzing local renal contrast density utilizing the Siemens Syngo body perfusion tool and correlated to the aorta. Cortical and medullary BF were 709±41 and 251±50 ml/100ml/min respectively in non-escaped rats. Cortical BF in escaped rats was similar (588±81 ml/100ml/min), but medullary BF was increased compared to non-escaped rats (666±105 ml/100ml/min). Blood volumes were similar in the two groups in cortex (42±1 vs. 49±6 ml/100ml), but elevated in the medulla of escaped rats (70±3 vs 18±3 ml/100ml).
Our results demonstrate that escape is accompanied by markedly elevated renomedullary BF and volume. Elevated BF to the renal medulla results in reduced interstitial osmolality, and may also contribute to the down-regulation of aquarporin-2 water channels known to accompany escape. These results therefore provide a potential mechanistic explanation for the reduced ability to concentrate urine during AVP escape.
Place, publisher, year, edition, pages
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-63692OAI: oai:DiVA.org:liu-63692DiVA: diva2:382226
American Society of Nephrology (ASN) 43rd Annual Meeting and Scientific Exposition, Denver, CO, USA.