AJP - Regulatory, Integrative and Comparative Physiology, Vol 238, Issue 5 311-R317, Copyright © 1980 by American Physiological Society
PAH transport in rock crab (Cancer irroratus) urinary bladder
C. W. Holliday and D. S. Miller
Crab urinary bladder appears to possess several morphological and
functional similarities to vertebrate renal proximal tubule. Sections of
intermolt rock crab bladder accumulated PAH by a process that was
concentrative (60 min tissue-to-medium ratio (T/M) for 10 microM PAH
averaged 24), Na dependent, powered by glycolytic metabolism, and
inhibitable by other organic anions. Initial section uptakes exhibited
saturation kinetics and a double-reciprocal plot of uptake vs.
concentration yielded a single line with a Km of 70 microM and a Vmax of 5
nmol . mg tissue-1 . h-1. Chlorophenol red and bromocresol green (BCG)
competitively inhibited PAH uptake. When bladder sheets were mounted in a
flux chamber, they exhibited a large, net lumen-to-serosa (L leads to S)
flux of 10 microM PAH that was abolished by 1 mM BCG. The small
unidirectional S leads to L flux was not BCG-inhibitable. Bladder sheets
exhibited PAH T/M greater than 1 after luminal, but not serosal, exposure.
BCG only reduced bladder sheet T/M after luminal exposure. The data are
consistent with uphill, Na-dependent, and carrier-mediated entry of PAH at
the luminal membrane and nonmediated exit at the serosal membrane.
