In:
American Journal of Physiology-Cell Physiology, American Physiological Society, Vol. 301, No. 6 ( 2011-12), p. C1458-C1469
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.
Type of Medium:
Online Resource
ISSN:
0363-6143
,
1522-1563
DOI:
10.1152/ajpcell.00293.2011
Language:
English
Publisher:
American Physiological Society
Publication Date:
2011
detail.hit.zdb_id:
1477334-X
SSG:
12
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