title: Ablation of the SERCA3 gene alters epithelium-dependent relaxation in mouse tracheal smooth muscle.
abstract: Sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase 3 (SERCA3), an isoform of the intracellular Ca(2+) pump that has been shown to mediate endothelium-dependent relaxation of vascular smooth muscle, is also expressed in tracheal epithelium. To determine its possible role in regulation of airway mechanical function, we compared tracheal contractility in gene-targeted mice deficient in SERCA3 (SERCA3(-)) with that in wild-type tracheae. Cumulative addition of ACh elicited concentration-dependent increases in isometric force (ED(50) = 2 microM, maximum force = 8 mN/mm(2)) that were identical in SERCA3(-) and wild-type tracheae. After ACh stimulation, substance P (SP) elicited a transient relaxation (42.6 +/- 3.2%, n = 28) in both tracheae. However, the rate of relaxation was significantly (P < 0.04, n = 9) more rapid in the wild-type [half-time (t(1/2)) = 34.3 s] than in the SERCA3(-) (t(1/2) = 61.6 s) trachea. The SP relaxation was reduced by rubbing the trachea, indicative of epithelial cell involvement. This was verified using a perfused trachea preparation. SP in the outside medium had no effect, whereas SP in the perfusate bathing the epithelial side elicited a relaxation. Nitric oxide synthase inhibition (0.2 mM N(omega)-nitro-L-arginine) reduced the SP relaxation by 36.5 +/- 12.5%, whereas the SP effect was abolished by eicosanoid inhibition (10 microM indomethacin). ATP also elicited an epithelium-dependent relaxation similar to SP but with a more rapid relaxation in the SERCA3(-) trachea than in the wild-type trachea. Our results indicate that SERCA3 gene ablation does not directly affect smooth muscle, which is consistent with the distribution of the isoform, but suggest that SERCA3 plays a role in epithelial cell modulation of airway smooth muscle function.
authors.affiliation: Department of Molecular and Cellular Physiology, Biochemistry, and Microbiology, University of Cincinnati College of Medicine, University of Cincinnati, Cincinnati, Ohio 45267-0576, USA.
authors.forename: J
authors.initials: J
authors.lastname: Kao
authors.forename: C N
authors.initials: CN
authors.lastname: Fortner
authors.forename: L H
authors.initials: LH
authors.lastname: Liu
authors.forename: G E
authors.initials: GE
authors.lastname: Shull
authors.forename: R J
authors.initials: RJ
authors.lastname: Paul
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D000252:Calcium-Transporting ATPases / Q000235:genetics*; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D004848:Epithelium / Q000502:physiology; D017353:Gene Deletion; D007527:Isoenzymes / Q000235:genetics; D051379:Mice; D009126:Muscle Relaxation / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D009994:Osmolar Concentration; D012016:Reference Values; D012519:Sarcoplasmic Reticulum / Q000201:enzymology*; D013373:Substance P / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects / Q000502:physiology*
chemical_list: D007527:Isoenzymes; D013373:Substance P; D000255:Adenosine Triphosphate; D013917:Thrombin; D000252:Calcium-Transporting ATPases; D000109:Acetylcholine