Isolated human colon strips as a pharmacological tool.

The spontaneous activity of isolated human colon strips was studied to obtain homogeneous results with a reproducible model. The strips of macroscopically normal appearance were mounted in an organ bath containing Krebs solution at 32 degrees C or Tyrode solution at 37 degrees C. Mechanical activity was recorded by an isometric transducer. Spontaneous motility did not occur in all preparations. Moreover, when observed, it could not always be evaluated. The percentage of strips with spontaneous activity was lower with Tyrode solution than with Krebs solution (65 vs. 81%). KC1 did not induce a plateau contraction. Acetylcholine induced concentration-dependent contractions, with a significantly different pD2: 4.43 +/- 0.39 and 5.59 +/- 0.16 for Krebs and Tyrode, respectively. Isoprenaline abolished spontaneous motility in Krebs solution. Only 20% of specimens presented evaluable motility. Krebs solution may be the best conditions for studying the effects of drugs on spontaneous motility, while Tyrode solution can be used to investigate the effects of contractile agents.