THE ROLE OF NOREPINEPHRINE IN THE REGULATION OF FLUID ABSORPTION IN THE RAT PROXIMAL TUBULE

  • 1 January 1980
    • journal article
    • research article
    • Vol. 215  (1) , 65-70
Abstract
In order to investigate the possibility of a direct effect of adrenergic transmitter on tubular fluid absorption, we have studied the effects of norepinephrine [NE] and phenoxybenzamine on fluid absorption in the proximal convoluted tubule of the rat kidney. Net fluid absorption (Jv) was determined in the same proximal convoluted tubule before and after addition of NE or phenoxybenzamine while the tubular lumen and peritubular capillaries were simultaneously microperfused in situ. When the tubular lumen was perfused with Ringer''s solution, and the peritubular capillaries were perfused with albumin Ringer''s solution, Jv was 2.85 .+-. 0.26 nl/mm .times. mm. Addition of 2 .times. 10-6 M NE to the capillary perfusate caused a 30% increase IN Jv which could be reversed by removing the adrenergic transmitter. The effect of NE was dose dependent with the maximal increase of Jv observed at a concentration of 10-5 M. Addition of 2 .times. 10-6 M phenoxybenzamine to the capillary perfusate caused a 16% decrease in Jv while the simultaneous administration of NE and phenoxybemzamine to the capillary perfusate caused a 25% decrease in Jv. There was no effect observed on JV when NE or phenoxybenzamine was added to the luminal perfusate. Adrenergic nerves may participate in the regulation of tubular fluid absorption through the direct action of NE on .alpha. adrenergic receptors located on the basolateral membrane of proximal tubular cells.