Effect of cold storage on the response of guinea-pig taenia coli to certain catecholamines and other agents

Relaxation produced by phenylephrine, epinephrine, norepinephrine and isoproterenol on guinea-pig taenia coli was not modified after cold storage of up to 6 days. These responses of the cold stored strip to phenylephrine, epinephrine and norepinephrine were prevented by pretreatment with alpha-blocking agents (phenoxybenzamine and phentolamine) but not by treatment with beta-blocking agents (propranolol and MJ 1999). The opposite was observed for the response to isoproterenol.On the other hand, the contraction produced by methacholine, (10⁻⁷ M), physostigmine (10⁻⁷ M), KCl (10 mM), and Ba (1 mM) was decreased after 3–6 days cold storage. Similarly, the relaxation produced by ATP (10⁻⁶ - 10⁻⁸ M) and 3',5'-cyclic AMP (10⁻⁴ - 10⁻⁵ was also decreased after 3−6 days cold storage; the response of fresh preparations to these agents was not prevented by either alpha- or beta-blocking drugs. In low Ca media (0.6 mM) catecholamine-induced relaxation of fresh strip was not changed, but that of ATP and 3',5'-cyclic AMP was decreased.These results indicate that cold storage does not interfere with the inhibitory system related to catecholamine but does with ATP and 3',5'-AMP. Also, prolonged cold storage does affect the membrane system involved in methacholine, KCl, Ba and physostigmine-induced contractions. This data suggests that the relaxation mechanisms of catecholamines may be different from that of exogenous high energy substances.