1. In man and in various animal species, absorption of NaCl from bile
by the gallbladder mucosa is associated with luminal proton secretion,
A similar absorption of NaCl in small intestine, colon and renal tubu
le is related, at least in part, to the presence of the NHE(3) isoform
of the Na+/H+ exchanger. This work was designed to find out whether N
HE(3) is also present in human gallbladder. 2. At surgery, 100-200 mg
of the gallbladder wall was obtained from patients treated by cholecys
tectomy for gallstones. After isolation of the mucosa, total RNA was e
xtracted and submitted to reverse transcription-polymerase chain react
ion with two primers: 5'-AAGCCICTGGTGCAGTGGCTGAAGG-3' and 5'-GGAGTCCTT
IAAGTCGGCIAAGCTGGGC-3', designed to amplify a sequence of 645 bp of ra
bbit NHE(3) mRNA (642 bp in man), RNA from human liver and from rabbit
heart, neither of which, contain NHE(3), and human ileal RNA, which d
oes contain NHE(3), were used as controls. 3. RNA extracted from the m
ucosal moiety of the gallbladder wall gave an amplification product of
about 645 nucleotides, Controls gave the expected negative or positiv
e results. Sequencing of the amplified RNA showed it was almost identi
cal to previously determined sequences of NHE(3) in other human tissue
s. 4. It is concluded that the mucosa of human gallbladder contains th
e mRNA of NHE(3) isoform. This isoform could therefore play a role in
sodium absorption from bile.