Flow dependence of K+ secretion in cortical distal tubules of the rat.
Superficial distal tubules were pump perfused (range 0-35 nl/min), generally with solutions similar in composition to early distal tubule fluid, in control, K+-depleted, acutely K+-loaded, and K+-adapted rats with the use of double-barreled resin-reference microelectrodes to measure K+ and Na+ activities and transepithelial potential differences (PD). When perfusion rate decreased from 35 to 5 nl/min in control animals, [K+] increased from 2 mM to between 10 and 20 mM, remaining at these levels as perfusion rate was decreased further. In low-K+ rats, the change in K+ activity with flow was greatly attenuated. In K+-loaded and K+-adapted rats, [K+] was higher than in controls at all flow rates. Na+ concentrations and lumen-negative PD increased with high flow rates in control rats. Addition of 10(-3) M amiloride blocked the increase in luminal K+ with low flow rates. In the physiological range of late distal flow rates, luminal [K+] remains constant and similar to the concentration attained in the steady state. At higher flow rates, [K+] declines, and K+ balance, PD, and Na+ reabsorption modulate the relationship between K+ secretion and flow rate.
Malnic
G
G
Department of Physiology, Yale University School of Medicine, New Haven, Connecticut 06510.
Berliner
R W
RW
Giebisch
G
G
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001826:Body Fluids / Q000502:physiology*; D004594:Electrophysiology; D066298:In Vitro Techniques; D007444:Inulin / Q000097:blood / Q000378:metabolism; D007672:Kidney Cortex; D007684:Kidney Tubules / Q000502:physiology*; D007686:Kidney Tubules, Distal / Q000378:metabolism / Q000502:physiology*; D009994:Osmolar Concentration; D010477:Perfusion; D011188:Potassium / Q000378:metabolism*; D011887:Raffinose / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology
D012965:Sodium Chloride; D000584:Amiloride; D007444:Inulin; D012964:Sodium; D011887:Raffinose; D011188:Potassium