Journal
AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY
Volume 307, Issue 11, Pages G1057-G1072Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpgi.00331.2014
Keywords
enteric; interstitial cells of Cajal; PDGFR alpha(+) cells; gastrointestinal; cGMP-dependent protein kinase
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Funding
- Zeiss confocal microscope [LSM510, 1 S10 RR16871]
- [DK078736]
- [P01DK041315]
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The effector cells and second messengers participating in nitrergic neuromuscular transmission (NMT) were investigated in the mouse internal anal sphincter (IAS). Protein expression of guanylate cyclase (GC alpha, GC beta) and cyclic GMP-dependent protein kinase I (cGKI) were examined in cryostat sections with dual-labeling immunohistochemical techniques in PDGFR alpha(+) cells, interstitial cells of Cajal (ICC), and smooth muscle cells (SMC). Gene expression levels were determined with quantitative PCR of dispersed cells from Pdgfr alpha(egfp/+), Kit(copGFP/+), and smMHC(Cre-egfp) mice sorted with FACS. The relative gene and protein expression levels of GC alpha and GC beta were PDGFR alpha(+) cells > ICC >> SMC. In contrast, cGKI gene expression sequence was SMC > ICC > PDGFR alpha(+) cells whereas cGKI protein expression sequence was neurons > SMC >> ICC = PDGFR alpha(+) cells. The functional role of cGKI was investigated in cGKI(-/)-mice. Relaxation with 8-bromo (8-Br)-cGMP was greatly reduced in cGKI(-/-) mice whereas responses to sodium nitroprusside (SNP) were partially reduced and forskolin responses were unchanged. A nitrergic relaxation occurred with nerve stimulation (NS, 5 Hz, 60 s) in cGKI(+/+) and cGKI(-/-) mice although there was a small reduction in the cGKI(-/-) mouse. N-omega-nitro-L-arginine (L-NNA) abolished responses during the first 20-30 s of NS in both animals. The GC inhibitor ODQ greatly reduced or abolished SNP and nitrergic NS responses in both animals. These data confirm an essential role for GC in NO-induced relaxation in the IAS. However, the expression of GC and cGKI by all three cell types suggests that each may participate in coordinating muscular responses to NO. The persistence of nitrergic NMT in the cGKI(-/)-mouse suggests the presence of a significant GC-dependent, cGKI-independent pathway.
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