Norepinephrines effect on adenosine transport in the proximal straight tubule

The effect of norepinephrine on C14-adenosine transport in the rabbit proximal tubule (S2) was studied. The transepithelial transport of adenosine (0.02 mM0 from lumin to bathing solution was measured by its rate of appearance (J/sub A/) in the bathing solution and by its disappearances (J/sub D/) from the luminal fluid. Norepinephrine (0.24 μM) was added to the bathing solution after a control flux period. After three samples from the experiment period the tubules were quickly harvested and the cellular concentration of C14-adenosine was determined. The high cellular adenosine concentration and th marked difference in adenosine appearance rate in the bathing solution compared to the luminal disappearance rate indicates the absorbed adenosine is trapped in the cells. This trapping may be due to adenosine metabolism or difficulty of crossing the basolateral membrane. Whichever is the case, norepinephrine appears to stimulate movement of adenosine or its metabolites into the bathing solution across the basolateral membrane