Intestinal smooth muscle dysfunction develops postnatally in cystic fibrosis mice.
OBJECTIVE
Intestinal dysmotility is one of the effects of cystic fibrosis (CF), but when and how this develops is not well understood. The goal of the present study was to use the Cftr knockout mouse to determine when in development circular smooth muscle of the small intestine becomes dysfunctional.


METHODS
Wild-type (WT) and CF mice were used at postnatal day 5 (P5) through adult. Pieces of small intestine were used to measure contractile activity of the circular muscle. Bacterial overgrowth was measured by quantitative polymerase chain reaction (PCR) of the bacterial 16S gene. Intestinal gene expression was determined by quantitative reverse transcription polymerase chain reaction (RT-PCR). Prostaglandin E2 (PGE2) and its metabolites were measured by enzyme immunoassay.


RESULTS
CF circular muscle response to cholinergic stimulation was similar to WT at P5, became somewhat impaired at P7, and was severely impaired by P14. In the CF intestine, bacterial overgrowth occurred by P4 and was maintained into adulthood. Eicosanoid metabolic gene expression in the CF intestine did not differ from WT shortly after birth. The phospholipase A2 genes, Pla2g4c and Pla2g5 exhibited increased expression in CF mice at P24. Prostaglandin degradative genes, Hpgd and Ptgr1, showed lower expression in CF as compared with WT at P16 and P24, respectively. PGE2 levels were significantly greater in CF mice at most ages from P7 through adulthood.


CONCLUSIONS
The results clearly demonstrate that lack of CFTR itself does not cause smooth muscle dysfunction, because the circular muscle from P5 CF mice had normal activity and dysfunction developed between P7 and P14.
University of Kansas School of Medicine, Anatomy and Cell Biology, Kansas City, KS 66160, USA. rdelisle@kumc.edu
Robert C
RC
De Lisle
Lauren
L
Meldi
Racquel
R
Mueller
D000818:Animals; D001419:Bacteria / Q000254:growth & development; D018678:Cholinergic Agents; D003550:Cystic Fibrosis / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics / Q000378:metabolism*; D015232:Dinoprostone / Q000378:metabolism; D005772:Gastrointestinal Transit / Q000235:genetics / Q000502:physiology*; D015870:Gene Expression; D007410:Intestinal Diseases / Q000378:metabolism / Q000382:microbiology / Q000503:physiopathology*; D007421:Intestine, Small / Q000378:metabolism / Q000382:microbiology / Q000503:physiopathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018181:Mice, Inbred CFTR; D018345:Mice, Knockout; D009119:Muscle Contraction / Q000235:genetics; D009130:Muscle, Smooth / Q000503:physiopathology*; D054467:Phospholipases A2 / Q000235:genetics / Q000378:metabolism
D018678:Cholinergic Agents; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D054467:Phospholipases A2; D015232:Dinoprostone