In mammals arginine-vasopressin (AVP) is a major hormone involved in the regulation of renal water reabsorption, acting via the increase of the osmotic permeability of the epithelium of the collecting duct. The AVP-induced intracellular events include, as a core step, the trafficking of the vesicles containing the water channels, aquaporin-2, to the apical plasma membrane of the collecting duct’s principal cells. The interstitium of the renal inner medulla contains abundant linear negatively charged glycosaminoglycan, hyaluronan (HA), which affects the water flow between structures of the concentrating mechanism, depending on its polymeric state. Using real-time RT-PCR, we tested the assumption that the renal hyaluronan may be involved in the long-term vasopressin effect on water reabsorption. The expression of the genes encoding hyaluronan synthase-2 (Has2), hyaluronidase-1, and hyaluronidase-2 (Hyal1 and Hyal2) in the kidneys of Wistar Albino Glaxo (WAG) was studied. The Has2 mRNA content was the highest in the papilla of the kidneys of the hydrated rats. The V2 receptor-selective vasopressin analog dDAVP (100 μg/kg of body weight, twice a day intraperitoneally for 2 days) induced a considerable decrease in the Has2 mRNA content in the papilla with less pronounced changes in the cortex. In contrast to Has2, the dDAVP treatment caused a significant increase in the Hyal1 and Hyal2 mRNA content in the renal papilla. There was a good fit between the Hyal1 and Hyal2 transcriptional levels and changes in hyaluronidase activity in the renal tissue. It was suggested that vasopressin is able to inhibit the synthesis of hyaluronan and concomitantly promotes its degradation in the renal papilla interstitium, thereby facilitating water flow between the elements of the renal countercurrent system. The implications for this effect are discussed in the context of the data in the literature.
- gene expression
- water reabsorption