Chung Ho Yeum

Increased expression of aquaporin water channels in hypothyroid rat kidney.

The present study was aimed to determine the molecular mechanisms underlying the water retention associated with hypothyroidism. Male Sprague-Dawley rats (200-220g) were experimentally induced of hypothyroidism by treatment with methimazole in drinking water (0.04%) for 8 weeks. In the experimental group, serum concentrations of thyroxine and triiodothyronine were significantly decreased. The expression of aquaporin 2 (AQP2) was significantly increased in the cortex, outer medulla, and inner medulla of the kidney. The expression of AQP1 as well as that of AQP3 was significantly increased in the cortex, though not in the medulla. The adenylyl cyclase activity provoked by arginine vasopressin (AVP), sodium fluoride, or forskolin was blunted in the hypothyroid kidney, while plasma levels of AVP were not significantly changed. The increased expression of AQP1-3 channels may in part account for the water retention in hypothyroidism.

The Predictive Parameters of Erythropoietin Hyporesponsiveness in Patients on Continuous Ambulatory Peritoneal Dialysis

Background: The present study was aimed at investigating the predictive parameters of erythropoietin (epoetin) hyporesponsiveness in patients on continuous ambulatory peritoneal dialysis (CAPD). Methods: We studied 40 patients with end-stage renal disease who had been receiving CAPD for at least 6 months and epoetin therapy for at least more than 2 months. Pearson’s simple correlation and multiple stepwise linear regression analysis was used to discover what parameter can predict epoetin resistance. We expressed epoetin resistance index (ERI) as ‘weekly epoetin dose/hematocrit/body weight’. The dose of epoetin is titrated by about 25% every 2 to 4 weeks to maintain a target hematocrit level between 33% and 36%. Results: We analyzed the relationship between ERI and other predictive parameters by Pearson’s correlation. These results showed ERI has a statistically significant correlation with transferrin saturation (TS) (r=−0.327, p=0.042), total weekly Kt/Vurea (r=−0.423, p=0.018), serum albumin level (r=−0.458, p=0.003), normalized protein catabolic rate (nPCR) (r=−0.479, p=0.006), normalized protein equivalent of total nitrogen appearance (nPNA) (r=−0.488, p=0.005) and serum C-reactive protein (CRP) (r=0.332, p = 0.036). Regression analysis was performed using stepwise linear regression for multiple variables to discover the most independent variable which is correlated with ERI. ERI was entered as a dependent variable, whereas the other parameters (age, duration of peritoneal dialysis, serum albumin level, CRP, serum ferritin, total weekly Kt/Vurea, nPCR, nPNA, serum iPTH, serum aluminium, TS) were entered as independent variables. This analysis showed CRP is the most significant variable and, if CRP is excluded, nPNA is the significant variable. CRP has a statistically significant correlation with serum albumin level (r=−0.418, p=0.007) and total weekly Kt/Vurea (r=−0.366, p=0.043). High CRP group has more increased level of ERI (p<0.05), age (p<0.05) and serum creatinine level (p<0.05) than normal control, but more decreased level of serum albumin (p<0.01) and serum iron levels (p<0.05). Conclusion: These results indicate that CRP is the most important predictor of epoetin hyporesponsiveness.

Percutaneous catheterization of the internal jugular vein for hemodialysis.

Objectives The present study was aimed at evaluating the clinical experiences in the internal jugular venous catheterization for hemodialysis. Methods We retrospectively analyzed the data on internal jugular venous catheterization at Chonnam National University Hospital from May 2000 to Februrary 2001. Results There were 132 uremic patients with a total of 150 attempts of internal jugular cannulation. Overall success rate was 90.9% with average puncture trials of 2.3±2.1. 124 (82.7%) of the catheterization attempts were made on the right side and 26 (17.3%) were made on the left. The catheters were left in place from 2 to 87 days with an average of 19.5±15.3 days per catheter. The dialysis sessions per catheter were from 2 to 58 with an average of 11.3±6.8. The mean blood flow during hemodialysis immediately after catheterization was 213.4±42.2 ml/min. Thirty two (21.3%) patients had early complications. These included carotid artery puncture (11.3%), local bleeding (4.7%), local pain (3.3%), neck hematoma (0.7%) and malposition of the catheter (1.3%). Seventeen (11.3%) patients had late complications. These included fever or infection (11.3%), inadequate blood flow rate (3.3%) and inadvertent withdrawal (2.0%). There was no catheter-related mortality. Conclusions Our experiences revealed that the internal jugular vein catheterization is relatively safe and efficient for temporary vascular access for hemodialysis.

Diminished Expression of Aquaporin Water Channels in Ureteral-obstructed Kidney in Rats

Objective: We investigated whether regulation of aquaporin (AQP) water channels is altered in the ureteral-obstructed kidney. Material and Methods: Male Sprague-Dawley rats were unilaterally obstructed of their left proximal ureters for 48 r h. The protein expression of AQP1-3 channels was determined in the kidney by Western blot analysis. The expression of AQP2 was also determined by immunohistochemistry. In order to specifically determine primary impairment of the pathway leading to an altered regulation of AQP channels stimulated by the arginine vasopressin (AVP)/cyclic adenosine monophosphate (cAMP) pathway, the catalytic activity and protein expression of different parts of the adenylyl cyclase complex were separately determined. Results: In the previously obstructed kidney, urinary osmolality and free water reabsorption were greatly decreased. The expression of AQP2 proteins was decreased in the cortex, outer medulla and inner medulla. Immunohistochemistry also showed a marked decrease in AQP2 expression. The expression of AQP1 and AQP3 was decreased in the outer medulla and inner medulla. cAMP generation in response to AVP, sodium fluoride or forskolin was greatly decreased. The expression of Gs ! and adenylyl cyclase VI proteins was decreased. The contralateral kidney showed minimal or no changes in these parameters. Conclusions: The reduced abundance of AQP water channels may at least partly account for the urinary concentration defect in the ureteral-obstructed kidney. The primary point of impairment of AQP channels regulated by the AVP/cAMP pathway may lie at the level of the catalytic unit of adenylyl cyclase.