The effect of short chain fatty acids (SCFA) on feline colonic smooth muscle contraction was evaluated in vitro. Colonic tissue was obtained from seven healthy male and female adult cats and seven healthy male and female kittens. Longitudinal and circular colonic smooth muscle strips from proximal and distal colon were incubated with SCFA (acetate, butyrate and propionate; 1-100 mM). SCFA-induced contractions were compared to responses obtained using maximal concentrations (10-4 M) of acetylcholine (ACh). The calcium dependence of the SCFA response was investigated by incubating with nifedipine (1 μM) or verapamil (1 μM). Acetate, butyrate and propionate elicited isometric stress responses (0.25-1.98× 104 N/ m2) in longitudinal, but not circular, smooth muscle from both the proximal and distal colon of adult cats. Maximal responses were attained at 50 and 100 mM SCFA. Maximal butyrate and propionate responses were 29 and 19% of the maximal ACh response (10-4 M), respectively. Acetate was least effective in stimulating contractile responses. Nifedipine and verapamil abolished all responses. Contractile responses in kittens were similar to those observed in adult cats, but were smaller in amplitude. Results of these studies have shown that SCFA stimulate longitudinal colonic smooth muscle contractions in kittens and adult cats in vitro. These SCFA-induced contractions involve activation of calcium influx. These in vitro findings may account for some of the effects of dietary fiber on feline colonic motility in vivo.
Bibliographical noteFunding Information:
The authors graciously acknowledge the financial support of the National Institutes of Health (T35 RR07065-001). An abstract of these data was presented at the 2002 ACVIM Forum in Dallas, TX. 1 The authors gratefully acknowledge the provision of animal tissue by Dr Mark Haskins of the University of Pennsylvania (NIH grant #s DK54481 and DK25759). 2 N -[2-hydroxyethyl] piperazine- N ′-[2-ethanesulfonic acid], Sigma Chemical Co, St Louis, MO. 3 Sylgard 184 silicone elastomer, Dow Corning, Midland, MI. 4 50-1569, 10-ml jacketed organ baths, Harvard Apparatus, South Natick, MA. 5 50-7905, isometric force transducers, Harvard Apparatus, South Natick, MA. 6 Acetyl-β-methylcholine bromide, Sigma Chemical Co, St Louis, MO. 7 HW-Model 800, Lakeshore Technologies, Chicago, IL. 8 SW-STP-8, Lakeshore Technologies, Chicago, IL. 9 Dell Optiplex GXMT 5166, Dell Computers, Austin, TX. 10 Sodium acetate, Aldrich Chemical, Milwaukee, WI. 11 Sodium butyrate, Aldrich Chemical, Milwaukee, WI. 12 Sodium propionate, Aldrich Chemical, Milwaukee, WI. 13 Nifedipine, Sigma Chemical Co, St Louis, MO. 14 Verapamil, Sigma Chemical Co, St Louis, MO.