Beta-agonist activation of an amiloride-insensitive transport mechanism in rabbit pleura.
The beta-agonist terbutaline increases the net rate of liquid absorption from hydrothoraces with albumin-Ringer solution: since beta-agonists decrease lymphatic drainage, the effect of terbutaline seems due to an increase in solute-coupled liquid absorption, (Zocchi et al. 1994 Respir. Physiol. 97:347-356). In this research we determined in anesthetized rabbits the rate of volume change in albumin-Ringer hydrothoraces of different size with amiloride plus terbutaline, and compared it with that previously obtained in hydrothoraces with amiloride alone. The net rate of liquid absorption was 0.09 ml/h greater (P < 0.01) with amiloride plus terbutaline than with amiloride alone. This indicates that terbutaline activates an amiloride-insensitive mechanism of Na+ transport. The increase in net rate of liquid absorption produced by terbutaline persisted with bumetanide 10(-6) M and SITS 10(-4) M, disappeared almost completely with bumetanide 10(-5) M, and completely with furosemide 10(-3) M. These findings suggest that the mechanism activated by terbutaline, when the amiloride-sensitive mechanisms of the pleura have been blocked, is a Na(+)-K(+)-2 Cl- or Na(+)-Cl- symport little sensitive to bumetanide.
Zocchi
L
L
Istituto di Fisiologia Umana I, Università di Milano, Italy.
Agostoni
E
E
Cremaschi
D
D
D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology; D005665:Furosemide / Q000494:pharmacology; D006876:Hydrothorax / Q000378:metabolism*; D017136:Ion Transport / Q000187:drug effects; D010994:Pleura / Q000378:metabolism*; D011817:Rabbits; D015222:Sodium Channels / Q000187:drug effects; D013726:Terbutaline / Q000037:antagonists & inhibitors / Q000494:pharmacology*
D015222:Sodium Channels; D002034:Bumetanide; D000584:Amiloride; D005665:Furosemide; D013726:Terbutaline