In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 106, No. 39 ( 2009-09-29), p. 16680-16685
Abstract:
Purinergic receptors are expressed in the membrane of the follicular cell layer that communicates with the Xenopus oocyte. Adenosine (Ado) generates a cAMP-dependent K + current ( I K,cAMP ), whereas ATP activates a Cl − current ( F Cl ) and has a dual effect on I K,cAMP , provoking both its activation and inhibition. Here, purinergic responses were studied electrophysiologically, first in the whole follicle ( w.f. ), and then in the same follicle after removal of its epithelium/theca layers ( e.t.r. follicle). Responses were analyzed as the ratio of the current amplitudes ( i etr /i wf ) in the two preparations. For ATP activation of I K,cAMP and F Cl , the ratios i etr /i wf were 0.053 and 22, respectively, whereas that for Ado was 0.75. Thus, epithelium/theca removal drastically altered the ATP response, suggesting a change in the signaling pathway that correlated with changes in the pharmacological characteristics: the half-maximal effective concentration for activation of the main current in w.f. ( I K,cAMP ) was 14 ± 3.8 μM [Hill coefficient ( nH ) = 2.7 ± 0.61], and that in e.t.r. follicles ( F Cl ) was 1.8 ± 0.68 μM ( nH = 0.76 ± 0.09), whereas Ado-response parameters did not change. Responses to UTP and β,γ-methylene-ATP, specific agonists for I K,cAMP inhibition and activation, respectively, indicated that in e.t.r. follicles inhibition increased and activation decreased drastically. Thus, purinergic responses were not independent; instead, they were functionally linked. We hypothesize that this property was due to direct interactions between receptors for Ado (A2 subtype) and ATP (P2Y subtype) in the Xenopus follicle.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.0905811106
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2009
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
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