Renomedullary and intestinal hyaluronan content during body water excess: a study in rats and gerbils

Abstract

Our previous studies in rats have suggested a role for renomedullary hyaluronan (HA) in water homeostasis. The gerbil is known for its unique ability to conserve water. In the present study renal papillary and intestinal HA were compared between groups of anaesthetized gerbils and rats before and after up to 6 h of i.v. water loading. Baseline papillary HA in gerbils was only 37 % of that in the rat. Water loading in rats increased the papillary HA content. Elevation was maximal (+27 %, P < 0.05) after 2 h of water loading and then declined to control levels after 6 h of water loading (+3 %, n.s.). In contrast, the gerbil responded with a decreased papillary HA content during water loading. The depression was maximal after 2 h (‐49 %, P < 0.05) and was still 41 % below the control values after 6 h (P < 0.05). The urine flow rate increased rapidly in the rat and its maximum, 21 times above the control level (P < 0.05), occurred at the HA peak, i.e. after 2 h of water loading while in the gerbil, the urine flow rate increased slowly and slightly and was only six times above control values after 6 h of water loading (P < 0.05). The HA content along the intestine was similar in the two species: lowest in the duodenum and jejunum and highest in the distal colon. To conclude, in the rat, the elevation of papillary interstitial HA during acute water loading would counteract water reabsorption by changing the physico‐chemical characteristics of the interstitial matrix favouring rapid water diuresis. This would work as a complement to the powerful regulation by ADH. The gerbil has a diametrically different regulation of papillary HA turnover during water loading. The decreased papillary HA level during water loading and the slow and small diuretic response may represent a genetic difference in adaptation to enhance the ability to conserve water in an arid environment.

Structure and Concentration Capacity of the Kidneys in Brattleboro Rats under Conditions of Long-Term Vasopressin Treatment

“…Long-term treatment of Brattleboro rats with arginine-VP was associated with not only activation of lysosomal hyaluronate hydrolases (β-glucuronidase served as an indicator of their status), but also with accumulation of HA in the renal medullary interstitium. The content of HA in the renal interstitium depends on activity of its biosynthesis in the interstitial cells, hyperosmolarity served as a factor stimulating this process [4]. In the present study, the significant increase in osmolarity of released urine under the effect of VP (Table 1) was presumably directly related to the increase in osmotic gradient in the medulla.…”

Hyaluronan synthases and hyaluronidases in the kidney during changes in hydration status

“…This differential distribution of HA is important for urine concentration and dilution, and as early as 1958, Ginetzinsky found evidence that the HA-degrading enzyme hyaluronidase is excreted in the urine in larger amounts during dehydration and drops to zero during hydration (Ginetzinsky, 1958). We have previously demonstrated that during acute hydration, papillary HA increases (Goransson et al, 2002;Hansell et al, 2000;Rugheimer et al, 2008a): an effect that can attenuate water reabsorption by changing the permeability characteristics of the interstitium. In contrast, papillary HA content decreases during water deprivation, indicating that the mechanisms by which HA regulates renal fluid balance differ from those of vasopressin (AVP), one of the major hormones involved in the regulation of renal fluid balance.…”

“…HA is predominantly found in the interstitium of the renal inner papilla (medulla): in the renal cortex, the HA content is very low, only a few percent of that in the renal papilla (Wells et al,1990;Johnsson et al, 1996;Hansell et al, 2000;Goransson et al, 2002;Rugheimer et al, 2008a). This differential distribution of HA is important for urine concentration and dilution, and as early as 1958, Ginetzinsky found evidence that the HA-degrading enzyme hyaluronidase is excreted in the urine in larger amounts during dehydration and drops to zero during hydration (Ginetzinsky, 1958).…”

The effects of different inhibitory pathways of prostaglandin E2 biosynthesis on renomedullary interstitial cells in rats: a multidisciplinary study

“…The high concentrations of HA in the kidney medulla support tubules and blood vessels and it is important for urine concentration [22]. HA also has a wondrous renal water handling capacity which is important for maintaining the concentration gradient and affects water transport in renal medulla [21][22][23].…”

“…However, studies suggest that, this inhibition leads to RMIC apoptosis [15][16][17][18][19][20]. Furthermore, hyaluronan (HA) which is a negatively charged glycosaminoglycan (GAG) found in renal interstitium and in the synthesis by RMICs, may play an important role in maintaining of water homeostasis [21,22]. The high concentrations of HA in the kidney medulla support tubules and blood vessels and it is important for urine concentration [22].…”