Mariko Hirai

Cytochrome P450 4A expression and arachidonic acid omega-hydroxylation in the kidney of the spontaneously hypertensive rat.

20-Hydroxyeicosatetraenoic acid (20-HETE) is a major arachidonate metabolite in the kidney of the spontaneously hypertensive rat (SHR). The increase in its synthesis has been associated with the elevation of blood pressure in the SHR. The omega-hydroxylation of arachidonic acid is an activity associated with members of the CYP4A gene family which, in the rat, comprises three major isoforms: 4A1, 4A2 and 4A3. 20-HETE displays potent and diverse biological activities which can affect pro- and anti-hypertensive mechanisms dependent upon where, when and by which isoform it has been produced. Therefore, it is important to identify and characterize its biosynthetic system. We compared CYP4A mRNA and protein expression to patterns of 20-HETE synthesis in the SHR kidney. The reverse transcription/polymerase chain reaction (RT/PCR) technique was used to amplify CYP4A mRNA in microdissected nephron segments. Southern blot hybridization of PCR products obtained from nephron segments with the CYP4A1 cDNA probe demonstrated strong signals in S2 and S3 segments of the proximal tubule. Immunoblots of nephron segments using a polyclonal anti-rat liver CYP4A1 antibody which cross-reacts with CYP4A2 and CYP4A3, and 14C-arachidonic acid metabolism, confirmed that arachidonic acid omega-hydroxylation, i.e., 14C-20HETE formation, and CYP4A proteins were also localized mainly in the S2 and S3 segments. Correlation also existed between the age-dependent increase in arachidonate omega-hydroxylation in the kidney and CYP4A mRNA levels as measured by Northern hybridization of total RNA using the CYP4A1 cDNA probe. Immunoblot analysis revealed that at 7 weeks, where 20-HETE production is at its maximum, all three proteins are expressed. CYP4A3 and 4A1 immunoreactive proteins appeared at 3 weeks, showed maximum levels at 5 and 7 weeks, respectively, and gradually decreased to lower levels at 13 and 20 weeks, whereas CYP4A2 levels were undetectable at 3, 5 and 7 weeks but appeared at 13-20 weeks. Additional immunoblots indicated that renal cortical CYP4A1 protein levels were higher in SHR compared to Sprague-Dawley and Wistar-Kyoto rats. The increased levels of CYP4A1-immunoreactive band at 7 weeks corresponded to the maximal activity of arachidonate omega-hydroxylation. Thus, CYP4A1 might play a significant role in contributing to the increased cortical/proximal production of 20-HETE seen in 7-week-old SHR. However, given the high homology among members of the CYP4A gene family and the lack of specific tools to discern among these isoforms, additional studies have to be carried out to substantiate our findings.

Quenching the Thirst in Dialysis Patients

In a double-blind cross-over trial, 22 stable end-stage renal failure patients on maintenance haemodialysis were subjected to conventional dialysis with dialysate containing 137 mEq/l sodium and constant ultrafiltration (UF) and to a different dialysis therapy, in which, by linear sodium modelling, the dialysate sodium was reduced from 137 to 128 mEq/l. A computerized UF program was used to gradually reduce the UF to a minimum towards the end of the session. Severity of thirst, interdialytic weight gain and intradialytic complications were less with low sodium dialysate. It allowed adequate UF with absolute hemodynamic stability. The reduced incidence of complication with low sodium dialysate therapy was probably because they required less UF.

Effect of a Nonpeptide Vasopressin V1 Antagonist (OPC-21268) on Experimental Accelerated Focal Glomerulosclerosis

The effects of the nonpeptide orally effective vasopressin V1 receptor antagonist OPC-21268 were studied in progressive focal glomerulosclerosis (FGS) which developed in spontaneously hypercholesterolemic (SHC) rats with manifestations of hypercholesterolemia and proteinuria. Unilateral nephrectomy was performed at 7 weeks of age to accelerate spontaneous FGS. After nephrectomy, OPC-administered rats were fed chow containing 1% OPC-21268 for 9 weeks. Treatment with vasopressin V1 antagonist significantly reduced the rate of increase in the levels of triglyceride, systolic blood pressure, serum creatinine and BUN, and prevented a significant deterioration in creatinine clearance. Rats were sacrificed at 16 weeks of age. Histologically, the index of glomerular sclerosis in the OPC group showed a significant decrease compared to that in the control group (2.2 +/- 0.1 vs. 2.6 +/- 0.1, p < 0.01). Relative interstitial volume and glomerular volume in the OPC group showed a tendency to decrease compared to those in the control group. These results indicate that vasopressin plays an important role through V1 receptors in the development of glomerulosclerosis, and vasopressin V1 antagonist may prevent the progression of renal injury in glomerulosclerosis.

Hypophosphatemia in End Stage Renal Disease

A case of hypophosphatemia in a 55-year-old black female on maintenance hemodialysis is described. She developed multiple bone fractures and congestive heart failure during her 10-year period on hemod

Membranous nephropathy complicating adenolymphoma of the parotid (Warthin's tumour).

Membranous nephropathy has been described in association with many malignancies including various lymphomas. However, it has not been previously described as a complication of benign solid adenolymphoma of the parotid, also called Warthins tumour. We describe a patient who presented with an adenolymphoma of the parotid, and developed a severe nephrotic syndrome due to membranous nephropathy 6 months after the parotid swelling. The nephrotic syndrome resolved following parotidectomy and a short course of immunosuppression with prednisolone and cyclophosphamide. The possible pathophysiologic mechanisms are discussed.

Significance of lymphocyte fatty acid changes in chronic renal failure

In the present study we describe fatty acid fluctuations in peripheral blood lymphocytes of patients with chronic renal failure who were undergoing maintenance hemodialysis. The decreased concentrations of linoleic acid and arachidonic acid and the increase in stearic acid are discussed in relation to the lymphocyte immune response and lymphocyte membrane enzymic systems in the disease.

Combination of vasopressin and angiotensin inhibition in experimental focal glomerulosclerosis

Summary: This study was designed to investigate the role of vasopressin and angiotensin II in the pathogenesis of focal glomerulosclerosis (FGS). A non‐peptide vasopressin VI antagonist (OPC‐21268) and an angiotensin converting enzyme inhibitor (ACE‐I) were administered either alone or in combination for 15 weeks to FGS, spontaneously hypercholesterolaemic rats. Treatment with the V1 antagonist (1% OPC‐21268) suppressed the rise in systolic blood pressure (SBP), serum triglyceride (TG), blood urea nitrogen (BUN) and serum creatinine (S‐Cr) levels, but not the elevations of urinary protein excretion (UPE) or serum total cholesterol (TC) levels. Morphologically, V1 antagonist significantly prevented an increase in the index of glomerular sclerosis (IS) and relative interstitial volume (RIV). In the low dose/high dose of V1 antagonist supplementation, the administration of 0.2% OPC‐21268 failed to suppress any increase in the SBP and TG levels, but significantly preserved renal function and attenuated renal lesions. In the combination study, rats were divided into four groups: (i) V1 antagonist (1% OPC‐21268); (ii) ACEI (imidapril, 5 mg/kg/per day); (iii) both treated groups; and (iv) an untreated control group. Angiotensin‐converting enzyme inhibitor significantly suppressed increases in SBP, UPE, TC, BUN, and S‐Cr levels compared with V1 antagonist. the combination therapy significantly enhanced these effects. Both agents significantly reduced IS and RIV, and combination therapy further reduced these levels. the results indicated that vasopressin, as well as angiotensin II, via the V1 receptor cause hypertension and renal injury in FGS rats. Vi antagonist and ACE‐I have antihypertensive and renoprotective effects in this FGS model, and enhanced their beneficial effects when used as combination therapy.

Sex Chromosomes Do Not Influence Renal Injury in Borderline Hypertensive Rats

The present study was undertaken to investigate whether the development of proteinuria in the borderline hypertensive rat (BHR) is influenced by the Y chromosome and to determine if the onset of prote