AJP - Renal Physiology, Vol 270, Issue 2 263-F274, Copyright © 1996 by American Physiological Society

ARTICLES

Upregulated renal adenosine A1 receptors augment PKC and glucose transport but inhibit proliferation

R. Coulson, P. S. Proch, R. A. Olsson, C. E. Chalfant and D. R. Cooper
Department of Veterans Affairs, James A. Haley Veterans Hospital, Tampa, Florida 33612, USA.

Adenosine A1 receptor densities were increased in cultured LLC-PK1 and OK cells by chronic treatment with the adenosine receptor antagonists 1,3,7-trimethylxanthine (caffeine, 1 mM) and 1,3-dimethyl-8-cyclopentylxanthine [cyclopentyltheophylline (CPT), < or = 0.4 mM], respectively. The A1 receptor number per cell was increased twofold by 10-day treatments with 1 mM caffeine or 0.1 mM CPT, and the sodium-coupled glucose uptake was augmented twofold by 1 mM caffeine and sevenfold by 0.1 microM CPT (higher doses of CPT were progressively less stimulatory). Glucose uptake was blocked by acute (2-h) treatment with CPT, adenosine deaminase, or calphostin C. Caffeine (1 mM) or CPT (> or = 0.1 mM) inhibited cell proliferation for the first 10 days, then cell growth assumed a normal proliferative rate despite continued presence of antagonist. Cytosolic protein kinase C (PKC) beta-isoform immunoactivity and PKC-beta II mRNA were elevated at least twofold during 10 days of 0.1 mM CPT or 1 mM caffeine treatment. The sustained elevation in sodium-glucose symport and PKC activity observed with adenosine receptor antagonists was similar to acute (2-h) effects of the adenosine A1 agonist R(-)-N6-phenylisopropyladenosine (R-PIA, 0.1-1 microM). Moreover, cell proliferation was increased by adenosine (0.1 microM R-PIA), whereas Na-K-adenosinetriphosphatase activity was unaltered with chronic antagonist or acute adenosine treatments. Caffeine treatment may have some non-adenosine A1 receptor-mediated actions, because it slightly (30%) augmented protein kinase A activity. It is concluded that chronic exposure of proximal tubule cells to caffeine or CPT augments PKC and sodium-glucose transport but retards cell proliferation mainly via adenosine A1 receptor-mediated mechanisms.

This article has been cited by other articles:

				V. Vallon, B. Muhlbauer, and H. Osswald Adenosine and kidney function. Physiol Rev, July 1, 2006; 86(3): 901 - 940. [Abstract] [Full Text] [PDF]

				H. T. LEE and C. W. EMALA Protein Kinase C and Gi/o Proteins Are Involved in Adenosine- and Ischemic Preconditioning--Mediated Renal Protection J. Am. Soc. Nephrol., February 1, 2001; 12(2): 233 - 240. [Abstract] [Full Text]