Mk. Barry et al., LUMINAL ADRENERGIC AGENTS MODULATE ILEAL TRANSPORT - DISCRIMINATION BETWEEN ALPHA-1 AND ALPHA-1 RECEPTORS, The American journal of surgery, 167(1), 1994, pp. 156-162
Luminal alpha-adrenergic agonists alter deal water, ion, and glucose t
ransport by a local mechanism. This study tested the hypothesis that l
uminal adrenergic agents modulate deal transport selectively, via spec
ific alpha(1) and alpha(2) receptors. Absorption studies (n = 72) were
performed on dogs with 25-cm ileal Thiry-Vella fistulas (TVF). Perfus
ion with (C-14) polyethylene glycol was used to calculate absorption o
f water, ions, and glucose from the TVF. Experiments included four 1-h
our periods. Agonists used were phenylephrine (alpha(1)), clonidine (a
lpha(2)), and norepinephrine (alpha(1) > alpha(2) and beta). Antagonis
ts used were terazosin (alpha 1) and yohimbine (alpha(2)). Phenylephri
ne and norepinephrine caused significant increases in water and ion ab
sorption (p<0.05). Clonidine caused significant decreases in water, io
n, and glucose absorption (p<0.05). Terazosin and yohimbine had no eff
ect alone. Terazosin prevented the proabsorptive effect of phenylephri
ne and norepinephrine, and yohimbine blocked the prosecretory effect o
f clonidine. Yohimbine significantly increased the norepinephrine-indu
ced proabsorptive effect. Luminal alpha-adrenergic agents selectively
modulate deal transport. Alpha(1)-receptor activation causes a proabso
rptive response, whereas alpha(2)-receptor activation causes a prosecr
etory response. The combination of a luminally administered mixed alph
a- beta-adrenergic agonist (norepinephrine) with alpha(2) receptor blo
ckade (yohimbine) may prove useful in pathologic secretory states such
as intestinal transplants, diabetic diarrhea, or diarrhea-associated
endocrinopathies.