Direct assessment of tubuloglomerular feedback responsiveness in connexin 40-deficient mice.

Participation of connexin 40 (Cx40) in the regulation of renin secretion and in the tubuloglomerular feedback (TGF) component of renal autoregulation suggests that gap junctional coupling through Cx40 contributes to the function of the juxtaglomerular apparatus. In the present experiments, we determined the effect of targeted Cx40 deletion in C57BL/6 and FVB mice on TGF responsiveness. In C57BL/6 mice, stop-flow pressure (PSF) fell from 40.3 ± 2 to 34.5 ± 2 mmHg in wild-type (WT) and from 31 ± 1.06 to 26.6 ± 0.98 mmHg in Cx40-/- mice. PSF changes of 5.85 ± 0.67 mmHg in WT and of 4.3 ± 0.55 mmHg in Cx40-/- mice were not significantly different (P = 0.08). In FVB mice, PSF fell from 37.4 ± 1.5 to 31.6 ± 1.5 mmHg in WT and from 28.1 ± 1.6 to 25.4 ± 1.7 mmHg in Cx40-/-, with mean TGF responses being significantly greater in WT than Cx40-/- (5.5 ± 0.55 vs. 2.7 ± 0.84 mmHg; P = 0.002). In both genetic backgrounds, PSF values were significantly lower in Cx40-/- than WT mice at all flow rates. Arterial blood pressure in the animals prepared for micropuncture was not different between WT and Cx40-/- mice. We conclude that the TGF response magnitude in superficial cortical nephrons is reduced by 30-50% in mice without Cx40, but that with the exception of a small number of nephrons, residual TGF activity is maintained. Thus gap junctional coupling appears to modulate TGF, perhaps by determining the kinetics of signal transmission.

Assessment on pollution of Ochratoxin A in grain in China and its apoptosis effect on vitro-cultured human tubular kidney cells.

Ochratoxin A (OTA) is nephrotoxic, immunosuppressive, and teratogenic in many species and is a possible human carcinogen. In this study, we investigated the OTA pollution situations of grains in northern China and the signaling pathway that mediated OTA-induced apoptosis in human tubular kidney cells (HKCs). Samples of grains collected from three representative areas were determined by using high-performance liquid chromatography fluorescence method. The effects of OTA on cell apoptosis, caspase-3, Bax, and Bcl-2 expression, and phosphorylation of c-Jun NH(2) terminal kinase (JNK) were detected in cultured HKCs via flow cytometry (FCM), Hoechst 33258 staining, and Western blot. It showed that OTA pollution of edible grains was very common in north China. OTA could affect caspase-3, Bax, and Bcl-2 expression and increased cell apoptosis in cultured HKCs. The JNK signalling pathway might play an important role during these cellular events.

Prognostic value of nuclear area index in combination with the World Health Organization grading system for patients with renal cell carcinoma.

OBJECTIVES: To assess the diagnostic accuracy of the World Health Organization (WHO) grading system for renal cell carcinoma (RCC) in terms of nuclear size evaluation. Furthermore, the prognostic usefulness of the nuclear area index (NAI), a new nuclear morphometric parameter expressed as the mean nuclear area (MNA) ratio of cancer to normal tubular cells, is investigated. METHODS: Measurement of the nuclear areas of cancer and normal tubular cells was performed on the histologic slides from the 76 patients with RCC, and the distribution of MNA and NAI was compared among the WHO grades. The clinical usefulness of MNA, NAI, grade, and TNM categories for the prediction of the progression-free and cause-specific survival of the patients was examined. RESULTS: MNA for cancer cells and NAI significantly increased according to the grade. NAI was 1.0 or less in 9 of the 10 patients with G1 tumors and more than 1.0 in 12 of the 13 patients with G3 tumors, whereas the NAI ranged widely from 0.53 to 2.0 in 53 patients with G2 tumors. By multivariate analysis, including grade and TNM categories, NAI and MNA were independent variables for survival in all the patients as well as for cancer progression in localized disease. CONCLUSIONS: WHO G2 RCCs are actually composed of tumors with varying nuclear size, and the prognosis of the patients with G2 tumors varied as well. NAI could provide improved prognostic information for the patients with RCC, especially in G2 cases.

Assessment of tissue-level kidney functions with primary cultures.

Primary cultures of renal proximal tubule have become important tools for examination of the mechanisms and control of transepithelial transport processes. The utility of the culture preparations for study of integrated tissue functions depends upon their accurate expression of in vivo transport processes. Maintenance of differentiation in culture is enhanced by contractible collagen substratum. Epithelial monolayer primary cultures of flounder and chicken proximal tubule, prepared by enzymatic and mechanical maceration with differential centrifugation, exhibit functional properties at the tissue level that generally resemble known properties of the freshly isolated or in vivo proximal tubule. Transepithelial electrical resistances and potential differences are very similar or identical to those of intact tubules. Na+-dependent glucose transport, a hallmark of proximal tubule function, has the same properties in culture as the tissue in vivo. Similarly, where appropriate comparisons are possible, amino acid, uric acid, and organic anion and cation transepithelial transport processes are qualitatively very similar in culture and in vivo. These two non-mammalian primary proximal tubule culture systems adequately reflect in vivo function, and thus provide opportunities for experimental manipulation otherwise not available.

Purification of rat papillary collecting duct cells: functional and metabolic assessment.

Rat renal papillary collecting duct (PCD) cells were isolated using collagenase and hyaluronidase digestion and a three-step low-speed centrifugation. As assessed by binding of the lectin Dolichos biflorus and determination of vasopressin-sensitive adenylate cyclase and Na+-K+-ATPase, the enrichment of PCD cells over a crude papillary cell preparation was 1.8, 2.4, and 1.4, respectively. Microscopic evaluation indicated that the preparation was greater than 90% pure PCD cells. The isolated cells were viable as evident from the high K/Na ratio of intracellular electrolytes measured by electron probe analysis (5.3), from the high ATP/ADP ratio (2.15), and the metabolic response to alterations in Na transport. Exposure to 2 mM ouabain or removal of Na reduced O2 consumption by 25-35%; the uncoupler carboxylcyanide-m-chlorophenylhydrazone more than doubled O2 consumption. In the presence of 14 mM glucose and at a PO2 of 100 Torr the cells produced substantial quantities of lactate. This aerobic glycolysis may account for greater than 20% of the ATP production. In the presence of rotenone, glycolysis increased by 56% and was able to maintain the cellular ATP level at 65% of control. In the absence of any exogenous substrate PCD cells respired normally and had a close to normal ATP content, but lactate production was markedly decreased. These results demonstrate that viable PCD cells can be isolated from rat kidney. At normal PO2 and in the presence of D-glucose the cells show a substantial amount of aerobic glycolysis, although their mitochondrial respiration is not rate limiting. In the absence of glucose the cells derive the majority of their energy from an as yet unidentified endogenous substrate.