Effects of beta-cyclodextrin on water flow in urinary bladder isolated from the toad Bufo arenarum.

ORCE G.; CASTILLO G.; CHANAMPA Y.

Buenos Aires

Congreso; Reunión Anual de la Asociación Argentina de Farmacología Experimental (SAFE); 2007

Asociación Argentina de Farmacología Experimental (SAFE)

Effects of beta-cyclodextrin on water flow in urinary bladder isolated from the toad Bufo arenarum Orce G., Castillo G. and Chanampa Y. - Dept. Physiology and Neuroscience - INSIBIO (UNT-CONICET) - Junín 1229 - 4000 Tucumán - e-mail: orcegap@yahoo.com    The urinary bladder isolated from toads (TB) exhibits great similarity to mammalian transport epithelia, particularly those of the distal kidney tubule, and are extensively used in studying water transport processes. We measured the effect of beta-cyclodextrin,  (BCD, a cholesterol scavenger) on water passage across the TB exposed to an osmotic gradient (Jw) by a gravimetric technique, and cholesterol and PO43- (from phospholipids) by standard biochemical techniques in the membrane isolated by selective centrifugation. When present in the basolateral bath, although devoid of effect per se, BCD inhibited Jw in the TB exposed to oxytocin or norepinephrine (both of which increase the intracellular generation of cyclic AMP [cAMP] by interacting with membrane receptors) but did not alter the response to theophylline (THEO, which increases cAMP by inhibiting cyclic nucleotide phosphodiesterase, an intracellular enzyme that hydrolyzes cAMP). Exposure to BCD also reduced the membrane cholesterol/phospholipid ratio. The present data, together with previous results from our laboratory, confirm that the effect of agents that increase Jw by interacting with membrane receptors (which have been suggested to have a cholesterol-rich lipid environment in the membrane) are selectively altered by BCD-mediated cholesterol extraction from the cell membrane, whereas agents acting intracellularly are not affected by the alteration of the membrane lipid environment.