title: 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.
authors: Dept. of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA.
authors: Rose Ellen
authors: RE
authors: Dixon
authors: Fiona C
authors: FC
authors: Britton
authors: Salah A
authors: SA
authors: Baker
authors: Grant W
authors: GW
authors: Hennig
authors: Christina M
authors: CM
authors: Rollings
authors: Kenton M
authors: KM
authors: Sanders
authors: Sean M
authors: SM
authors: Ward
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005260:Female; D051379:Mice; D008807:Mice, Inbred BALB C; D009119:Muscle Contraction / Q000502:physiology*; D009130:Muscle, Smooth / Q000378:metabolism*; D010057:Oviducts / Q000502:physiology*; D018408:Patch-Clamp Techniques; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D002118:Calcium