Creep after loading in the relaxed and contracted smooth muscle (taenia coli of the guinea pig) under various osmotic conditions.

1. Experiments to investigate the creep phenomena of the taenia coli were performed in hypotonic (207 mosm) and hypertonic (447 or 463 mosm) media, in the relaxed (Ca2+-depletion + verapamil) as well as in the contracted (K2SO4-depolarized) state. They were compared with earlier results in isotonic media. The samples were standardized with respect to their volume (weight) before the beginning of the experiment. 2. Neither in the relaxed, nor in the contracted state was there a statistically significant difference in mean total length observed within each test series after loading with 9928 dyn for 2000 s (about 33 min) in the different osmotic media. We define total length as unloaded initial length lo + initial pure leastic extension lE + creep N. 3. In the contracted state the mean total lengths attained by elastic extension and creep are significantly greater than in the relaxed state in both hypotonic and isotonic media. The greater variance in the data for hypertonic solutions makes any statistical decision of this kind impossible. 4. The typical time course of creep (N) and particularly the hyperbolic dependance of N and dN/dt stated in an earlier paper could also be observed here under varied osmotic conditions. 5. The results suggest that the viscosity of the cell plasma is not significant for the time course and extent of creep in smooth muscles of vertebrates. Creep probably takes place in the solid structures of the cells: most particularly the contractile proteins may be involved.