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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 tubule is related, at least in part, to the presence of the NHE3 isoform of the Na+/H+ exchanger. This work was designed to find out whether NHE3 is also present in human gallbladder. 2. At surgery, 100–200 mg of the gallbladder wall was obtained from patients treated by cholecystectomy for gallstones. After isolation of the mucosa, total RNA was extracted and submitted to reverse transcription—polymerase chain reaction with two primers: 5′-AAGCCICTGGTGCAGTGGCTGAAGG-3′ and 5′-GGAGTCCTTIAAGTCGGCIAAGCTGGGC-3′, designed to amplify a sequence of 645 bp of rabbit NHE3 mRNA (642 bp in man). RNA from human liver and from rabbit heart, neither of which contain NHE3, and human ileal RNA, which does contain NHE3, were used as controls. 3. RNA extracted from the mucosal moiety of the gallbladder wall gave an amplification product of about 645 nucleotides. Controls gave the expected negative or positive results. Sequencing of the amplified RNA showed it was almost identical to previously determined sequences of NHE3 in other human tissues. 4. It is concluded that the mucosa of human gallbladder contains the mRNA of NHE3 isoform. This isoform could therefore play a role in sodium absorption from bile.

France is a non-endemic region for β thalassemia. In this country, the sporadic cases of Cooley's disease encountered affect almost constantly subjects of Mediterranean origin.In this report, we have screened, using oligonucleotide probes, the distribution of the main β thalassemia mutations present in the population of South-eastern France whose origins lie in the mixing of several Mediterranean ethnic groups. Among 105 β thalassemia chromosomes, we have observed a limited number of alleles, since, by using oligonucleotide probes for six mutations, we have characterized the molecular defect in 90 % of the chromosomes. The four main mutations were found in more than 85 % of the chromosomes and the others in about 5 %. The distribution of the β thalassemia mutations within the various ethnic groups was determined.

The absorption of water and electrolytes by the gallbladder seems to be largely dependent upon a Na+/H+exchange at the apical membrane of the gallbladder epithelium. To find out if the exchanger involved is the NHE3isoform, as in other absorbing epithelia, two studies were performed using the rabbit gallbladder. First, we studied 22Na absorption in Ussing chambers with Krebs buffer as a control solution, and in the presence of amiloride (100, 200 or 1000 μM), ethyl-isopropyl-amiloride (EIPA, 1 or 5 μM), or the phorbol ester, phorbol 12-myristate 13-acetate (PMA, 1 μM). A net mucosal-to-serosal Na+flux was observed with control buffer. No inhibition of this net flux was observed with 5 μM EIPA, and the IC50for amiloride was found to be 200 μM. PMA induced a reduction of absorption by 30% that was prevented by incubation with calphostin C. Resistance to amiloride and EIPA, and inhibition by PMA are consistent with the involvement of the NHE3isoform. The second study involved reverse-transcriptase polymerase chain reaction (RT-PCR) of total gallbladder RNA, with two primers designed to amplify a 645-base-pair fragment from NHE3mRNA. A cDNA fragment of the expected size was actually obtained from gallbladder RNA, while RT-PCR of RNA from the liver, which does not contain NHE3, gave negative results. A sequence of 492 nucleotides of the amplified product was determined, which was almost superimposable onto the known sequence of the corresponding fragment of rabbit NHE3. It is concluded that, in rabbit gallbladder, neutral NaCl absorption is, at least in part, dependent on the NHE3isoform of the Na+/H+exchanger.