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Electrical slow waves in the mouse oviduct are dependent on extracellular and intracellular calcium sources.


ABSTRACT: Spontaneous contractions of the myosalpinx are critical for oocyte transport along the oviduct. Slow waves, the electrical events that underlie myosalpinx contractions, are generated by a specialized network of pacemaker cells called oviduct interstitial cells of Cajal (ICC-OVI). The ionic basis of oviduct pacemaker activity is unknown. Intracellular recordings and Ca(2+) imaging were performed to examine the role of extracellular and intracellular Ca(2+) sources in slow wave generation. RT-PCR was performed to determine the transcriptional expression of Ca(2+) channels. Molecular studies revealed most isoforms of L- and T-type calcium channels (Cav1.2,1.3,1.4,3.1,3.2,3.3) were expressed in myosalpinx. Reduction of extracellular Ca(2+) concentration ([Ca(2+)](o)) resulted in the abolition of slow waves and myosalpinx contractions without significantly affecting resting membrane potential (RMP). Spontaneous Ca(2+) waves spread through ICC-OVI cells at a similar frequency to slow waves and were inhibited by reduced [Ca(2+)](o). Nifedipine depolarized RMP and inhibited slow waves; however, pacemaker activity returned when the membrane was repolarized with reduced extracellular K(+) concentration ([K(+)](o)). Ni(2+) also depolarized RMP but failed to block slow waves. The importance of ryanodine and inositol 1,4,5 trisphosphate-sensitive stores were examined using ryanodine, tetracaine, caffeine, and 2-aminoethyl diphenylborinate. Results suggest that although both stores are involved in regulation of slow wave frequency, neither are exclusively essential. The sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) pump inhibitor cyclopiazonic acid inhibited pacemaker activity and Ca(2+) waves suggesting that a functional SERCA pump is necessary for pacemaker activity. In conclusion, results from this study suggest that slow wave generation in the oviduct is voltage dependent, occurs in a membrane potential window, and is dependent on extracellular calcium and functional SERCA pumps.

SUBMITTER: Dixon RE 

PROVIDER: S-EPMC3233798 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature

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Electrical slow waves in the mouse oviduct are dependent on extracellular and intracellular calcium sources.

Dixon Rose Ellen RE   Britton Fiona C FC   Baker Salah A SA   Hennig Grant W GW   Rollings Christina M CM   Sanders Kenton M KM   Ward Sean M SM  

American journal of physiology. Cell physiology 20110831 6


Spontaneous contractions of the myosalpinx are critical for oocyte transport along the oviduct. Slow waves, the electrical events that underlie myosalpinx contractions, are generated by a specialized network of pacemaker cells called oviduct interstitial cells of Cajal (ICC-OVI). The ionic basis of oviduct pacemaker activity is unknown. Intracellular recordings and Ca(2+) imaging were performed to examine the role of extracellular and intracellular Ca(2+) sources in slow wave generation. RT-PCR  ...[more]

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