Isoforms of Na+, K+-ATPase in human prostate; specificity of expression and apical membrane polarization A. Mobasheri1, D. Oukrif2, S.P. Dawodu2, M. Sinha2, P. Greenwell2, D. Stewart3, M.B.A. Djamgoz3, C.S. Foster4, P. Martín-Vasallo5 and R. Mobasheri6 1Department of Veterinary Preclinical Sciences,
University of Liverpool, Liverpool, United Kingdom, Offprint requests to: Dr. A. Mobasheri, Department of Veterinary Preclinical Sciences, University of Liverpool, Liverpool L69 7ZJ, United Kingdom. Fax : +44 151 794 4243. e-mail: A.Mobasheri@liverpool.ac.uk
Summary. The cellular distribution of Na+, K+-ATPase subunit isoforms was mapped in the secretory epithelium of the human prostate gland by immunostaining with antibodies to the a and ß subunit isoforms of the enzyme. Immunolabeling of the a1, ß1 and ß2 isoforms was observed in the apical and lateral plasma membrane domains of prostatic epithelial cells in contrast to human kidney where the a1 and ß1 isoforms of Na+, K+-ATPase were localized in the basolateral membrane of both proximal and distal convoluted tubules. Using immunohistochemistry and PCR we found no evidence of Na+, K+-ATPase a2 and a3 isoform expression suggesting that prostatic Na+, K+-ATPase consists of a1/ß1 and a1/ß2 isozymes. Our immunohistochemical findings are consistent with previously proposed models placing prostatic Na+, K+-ATPase in the apical plasma membrane domain. Abundant expression of Na+, K+-ATPase in epithelial cells lining tubulo-alveoli in the human prostate gland confirms previous conclusions drawn from biochemical, pharmacological and physiological data and provides further evidence for the critical role of this enzyme in prostatic cell physiology and ion homeostasis. Na+, K+-ATPase most likely maintains an inwardly directed Na+ gradient essential for nutrient uptake and active citrate secretion by prostatic epithelial cells. Na+, K+-ATPase may also regulate lumenal Na+ and K+, major counter-ions for citrate. Histol. Histopathol. 16, 141-154 (2001) Key words: Na+,
K+-ATPase, Prostate, Immunohisto-chemistry, Membrane polarization,
Apical membrane, Polymerase chain reaction |