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  • Title: Additive effects of hypertension and diabetes on renal cortical expression of PKC-alpha and -epsilon and alpha-tubulin but not PKC-beta 1 and -beta 2.
    Author: Osicka TM, Russo LM, Qiu ML, Brammar GC, Thallas V, Forbes JM, Comper WD, Jerums G.
    Journal: J Hypertens; 2003 Dec; 21(12):2399-407. PubMed ID: 14654761.
    Abstract:
    OBJECTIVE: This study examined the separate and combined effects of hypertension and diabetes on renal cortical expression of protein kinase C (PKC) isoforms -beta 1, -beta 2, -alpha and -epsilon, to determine whether albuminuria is the result of an increase in the expression of one or a combination of PKC isoforms. Corresponding changes in renal microtubules were also assessed. METHODS: Diabetes (D) was induced in Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) by streptozotocin. After 24 weeks, PKC expression was determined by Western blot and microtubules were assessed by immunohistochemistry for alpha-tubulin protein. RESULTS: Diabetes was characterized by significant increases in glycated haemoglobin (HbA1c) as compared to controls (C). There was a significant increase of three- to four-fold in PKC protein content for all four isoforms in renal cortex from SHR-C and WKY-D, and similar and significant levels of albuminuria (approximately 10 mg/24 h) observed in these groups in comparison to WKY-C (approximately 1 mg/24 h). Interestingly, PKC-alpha and -epsilon but not PKC-beta 1 and -beta 2 protein content was doubled in SHR-D, and albuminuria increased tenfold (approximately 100 mg/24 h) in comparison to SHR-C and WKY-D. These changes were paralleled by a significant decrease in alpha-tubulin protein content of approximately 50% in SHR-C and approximately 33% in WKY-D compared to WKY-C, with a further decrease of approximately 67% in SHR-D compared to WKY-C. CONCLUSION: These findings indicate that PKC expression can be increased by either diabetes or hypertension, and that there are further specific increases in the expression of PKC isoforms -alpha and -epsilon in the model of combined diabetes and hypertension. In addition, the degree of disruption in microtubular cytoskeleton appears to be correlated with PKC activation and levels of albuminuria.
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