Objectives: 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.
Address correspondence and reprint requests to Robert C. De Lisle, PhD, Anatomy and Cell Biology, University of Kansas School of Medicine, MS 3038, 3901 Rainbow Blvd, Kansas City, KS 66160 (e-mail: firstname.lastname@example.org).
Received 22 March, 2012
Accepted 10 May, 2012
The present study was supported by the Cystic Fibrosis Foundation, a pilot project as part of P20 RR024214 COBRE on Molecular Regulation of Cell Development and Differentiation from the National Center for Research Resources, and NIH grant R21AI083479.
The authors report no conflicts of interest.