AJP - Regulatory, Integrative and Comparative Physiology, Vol 242, Issue 1 25-R29, Copyright © 1982 by American Physiological Society
PAH transport in rock crab urinary bladder. II. Luminal and serosal steps
C. W. Holliday and D. S. Miller
To characterize the organic anion transport properties of the luminal (1)
and serosal (s) membranes of crab urinary bladder, initial (10 min) fluxes
(J) and tissue accumulations (Ac) of 10 microM PAH were measured in the
absence and presence of 1 mM BCG (nontransported, high-affinity
competitor). Control bladders exhibited net reabsorptive transport with a
mean Jl leads to s/Js leads to 1 of about 7; concentrative transport of
p-aminohippuric acid (PAH) occurred only across the luminal cell (c)
membrane. With luminal PAH, luminal bromocresol green (BCG) reduced Jl
leads to c, Jc leads to s, and Ac by about 85%; serosal BCG reduced Jc
leads to s, increased Ac but had no effect on Jl leads to c. With serosal
PAH, serosal BCG reduced Js leads to c, Jc leads to l, and Ac; luminal BCG
had no effects on either fluxes or tissue accumulation. When bladder sheets
were loaded with radiolabeled PAH, mounted in a chamber, and exposed to
flowing crab Ringer solution on both sides, Jc leads to s was nearly twice
as large as Jc leads to l; BCG significantly reduced Jc leads to s but not
Jc leads to l. With unlabeled PAH in the efflux media, Jc leads to s was
increased. The data are consistent with a model featuring an inwardly
directed pump at the luminal membrane, a facilitated carrier at the serosal
membrane, and nonmediated pathways at both membranes.
