Effect of vasopressin on the expression of genes for key enzymes of hyaluronan turnover in Wistar Albino Glaxo and Brattleboro rat kidneys.

Hyaluronan (HA), the major glycosaminoglycan of the interstitial matrix, is heterogeneously distributed within the kidney. Using real-time RT-PCR, we tested the assumption that renal HA may be involved in the long-term effect of vasopressin on water reabsorption. The expression of the genes encoding hyaluronan synthase-2 (Has2), hyaluronidase-1 and hyaluronidase-2 (Hyal1 and Hyal2) was studied in the kidneys of Wistar Albino Glaxo (WAG) and homozygous vasopressin-deficient Brattleboro rats treated with the V2 receptor-selective vasopressin analogue dDAVP (100 μg (kg body wt)(-1), i.p., twice a day for 2 days). The Has2 mRNA content was the highest in the kidney papilla of the hydrated WAG and control Brattleboro rats, devoid of vasopressin. In WAG rats, dDAVP induced a considerable decrease in Has2 mRNA content in the papilla, with less pronounced changes in the cortex. The changes elicited by dDAVP in Brattleboro rats tended to be the same as in WAG rats, but weaker. In contrast to Has2, dDAVP treatment caused a significant increase in the Hyal1 and Hyal2 mRNA content in the renal papilla of WAG and Brattleboro rats. In rats of both strains, there was a good fit between Hyal1 and Hyal2 transcriptional levels and changes in hyaluronidase activity in the renal tissue. It is suggested that vasopressin is able to inhibit the synthesis of HA and concomitantly promote its degradation in the interstitium of the renal papilla, thereby facilitating water flow between elements of the renal countercurrent system. The implications for this effect are discussed in the context of the data in the literature.