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Proton secretion in the male reproductive tract: involvement of Cl--independent HCO-3 transport

Proton secretion in the male reproductive tract: involvement of Cl--independent HCO-3 transport
Proton secretion in the male reproductive tract: involvement of Cl--independent HCO-3 transport
The lumen of the epididymis is the site where spermatozoa undergo their final maturation and acquire the capacity to become motile. An acidic luminal fluid is required for the maintenance of sperm quiescence and for the prevention of premature activation of acrosomal enzymes during their storage in the cauda epididymis and vas deferens. We have previously demonstrated that a vacuolar H+-ATPase [proton pump (PP)] is present in the apical pole of apical and narrow cells in the caput epididymis and of clear cells in the corpus and cauda epididymis and that this PP is responsible for the majority of proton secretion in the proximal vas deferens. We now show that PP-rich cells in the vas deferens express a high level of carbonic anhydrase type II (CAII) and that acetazolamide markedly inhibits the rate of proton secretion by 46.2 +/- 6.1%. The rate of acidification was independent of Cl- and was strongly inhibited by SITS under both normal and Cl--free conditions (50.6 +/- 5.0 and 57. 5 +/- 6.0%, respectively). In the presence of Cl-, diphenylamine-2-carboxylate (DPC) had no effect, whereas SITS inhibited proton secretion by 63.7 +/- 11.3% when applied together with DPC. In Cl--free solution, DPC markedly inhibited proton efflux by 45.1 +/- 7.6%, SITS produced an additional inhibition of 18.2 +/- 6.6%, and bafilomycin had no additive effect. In conclusion, we propose that CAII plays a major role in proton secretion by the proximal vas deferens. Acidification does not require the presence of Cl-, but DPC-sensitive Cl- channels might contribute to basolateral extrusion of HCO-3 under Cl--free conditions. The inhibition by SITS observed under both normal and Cl--free conditions indicates that a Cl-/HCO-3 exchanger is not involved and that an alternative HCO-3 transporter participates in proton secretion in the proximal vas deferens.
carbonic anhydrase II, self-referencing proton-selective electrode, immunocytochemistry, hydrogen-adenosine 5?-triphosphatase
0363-6143
C1134-C1142
Breton, Sylvie
2e794185-ff02-4aef-a2b3-a390eb5552b5
Hammar, Katherine
c1706f67-2af6-4246-9c7f-341d48a693ec
Smith, Peter J.S.
003de469-9420-4f12-8f0e-8e8d76d28d6c
Brown, Dennis
6938f113-e019-4a94-b66a-ae244ae2e6d7
Breton, Sylvie
2e794185-ff02-4aef-a2b3-a390eb5552b5
Hammar, Katherine
c1706f67-2af6-4246-9c7f-341d48a693ec
Smith, Peter J.S.
003de469-9420-4f12-8f0e-8e8d76d28d6c
Brown, Dennis
6938f113-e019-4a94-b66a-ae244ae2e6d7

Breton, Sylvie, Hammar, Katherine, Smith, Peter J.S. and Brown, Dennis (1998) Proton secretion in the male reproductive tract: involvement of Cl--independent HCO-3 transport. American Journal of Physiology: Cell Physiology, 275 (4), C1134-C1142. (PMID:9755067)

Record type: Article

Abstract

The lumen of the epididymis is the site where spermatozoa undergo their final maturation and acquire the capacity to become motile. An acidic luminal fluid is required for the maintenance of sperm quiescence and for the prevention of premature activation of acrosomal enzymes during their storage in the cauda epididymis and vas deferens. We have previously demonstrated that a vacuolar H+-ATPase [proton pump (PP)] is present in the apical pole of apical and narrow cells in the caput epididymis and of clear cells in the corpus and cauda epididymis and that this PP is responsible for the majority of proton secretion in the proximal vas deferens. We now show that PP-rich cells in the vas deferens express a high level of carbonic anhydrase type II (CAII) and that acetazolamide markedly inhibits the rate of proton secretion by 46.2 +/- 6.1%. The rate of acidification was independent of Cl- and was strongly inhibited by SITS under both normal and Cl--free conditions (50.6 +/- 5.0 and 57. 5 +/- 6.0%, respectively). In the presence of Cl-, diphenylamine-2-carboxylate (DPC) had no effect, whereas SITS inhibited proton secretion by 63.7 +/- 11.3% when applied together with DPC. In Cl--free solution, DPC markedly inhibited proton efflux by 45.1 +/- 7.6%, SITS produced an additional inhibition of 18.2 +/- 6.6%, and bafilomycin had no additive effect. In conclusion, we propose that CAII plays a major role in proton secretion by the proximal vas deferens. Acidification does not require the presence of Cl-, but DPC-sensitive Cl- channels might contribute to basolateral extrusion of HCO-3 under Cl--free conditions. The inhibition by SITS observed under both normal and Cl--free conditions indicates that a Cl-/HCO-3 exchanger is not involved and that an alternative HCO-3 transporter participates in proton secretion in the proximal vas deferens.

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Published date: October 1998
Keywords: carbonic anhydrase II, self-referencing proton-selective electrode, immunocytochemistry, hydrogen-adenosine 5?-triphosphatase

Identifiers

Local EPrints ID: 190285
URI: http://eprints.soton.ac.uk/id/eprint/190285
ISSN: 0363-6143
PURE UUID: dd8215d4-fec0-49f6-aa32-f846d184806e
ORCID for Peter J.S. Smith: ORCID iD orcid.org/0000-0003-4400-6853

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Date deposited: 16 Jun 2011 13:04
Last modified: 21 Nov 2021 03:04

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Contributors

Author: Sylvie Breton
Author: Katherine Hammar
Author: Dennis Brown

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