Stimulation of autonomic nervous system affects intestinal function, and adrenergic agents stimulate ion absorption or secretion in several epithelia. In order to identify the role of adrenergic hormones on colonic ion transport we studied the effect of epinephrine (Epi), norepinephrine (NE) and isoproteronol (Iso) on short circuit current (Isc), potential differene (PD), J(Na)(net) and J(Cl)(net) across isolated rat colonic mucosa. Addition of Epi to serosal solution significantly reduced PD and Isc, and the threshold concentration for the decrease in PD and Isc was 10-7M. Maximal decrease in Isc (30.7 μA/cm2) was produced by 2 x 10-4M Epi. Km of the Epi induced change in Isc was 1.8 x 10-7M. NE and Iso produced similar decreases in PD and Isc and their Km and Vmax identical to those of Epi. 5 x 10-5M Epi produced a significant increase in both J(Na)(net) (2.87 ± 0.95 μEq/hr.cm2) and J(C6Xnet) (4.08 ± 0.73 μEq/hr.cm2). The nature of the decrement in Isc is uncertain since Epi produced a similar decrease in Isc in HCO3-free solution. The decrease in Isc produced by Epi was only partially prevented either by phenoxybenzamine (PB), or by propranolol (PR); PB produced a greater inhibition than PR. In contrast, PB plus PR completely blocked the effect of Epi on Isc. The effect of Iso on Isc was totally inhibited by PR but not by phentolamine. Atropine did not produce any significant blockade. Epi did not increase mucosal cyclic AMP content and the addition of exogenous cyclic AMP, cyclic GMP or their derivatives did not produce a decrease in PD and Isc. These results demonstrate that adrenergic hormones increase active Na and Cl absorption in the colon, and that the effect of epinephrine represents involvement of alpha and beta receptors. These observations provide direct evidence of both alpha and beta adrenergic control of colonic ion transport.
|Number of pages
|Scandinavian Journal of Gastroenterology
|Published - Jan 1 1978
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