Article

Distribution of beta-adrenoceptor subtypes in gastrointestinal tract of nondiabetic and diabetic BB rats. A longitudinal study.

Division of Gastroenterology, Hospital of the University of Pennsylvania, Philadelphia 19104, USA.
Digestive Diseases and Sciences (Impact Factor: 2.61). 07/1997; 42(6):1146-53.
Source: PubMed

ABSTRACT

The effects of aging and diabetes on the distribution of beta-adrenoceptor subtypes in the gut were investigated in the BB rat. [125I]Cyanopindolol binding to 10-micron sections was evaluated using film autoradiography. Cyanopindolol binding to beta-, beta 1-, and beta 2-adrenoceptors was displaced by 1 microM propranolol, 50 nM ICI-89-406, and 100 nM ICI-118-551, respectively. beta-Adrenoceptor binding was highest in the circular muscle of proximal colon and lowest in the pylorus of 4- to 5-month-old rats. Aging (8- to 10-month-old vs. 4- to 5-month-old rats) was associated with increased beta-adrenoceptor binding in the pylorus and reduced binding in the proximal colon. Diabetes had a time-dependent effect on the level of beta-adrenoceptor binding. It was increased in the antral and pyloric stomach but longer periods of diabetes caused a reduction in beta-adrenoceptor binding in the pylorus. Those in the intestine were reduced time-dependently and involved beta 1- or beta 2-adrenoceptors or both.

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    • "In addition , the dopamine - induced increase in intracellular cAMP levels is much higher in β 2 - adrenoceptor - transfected COS - 7 cells than that in COS - 7 cells transfected with β 1 - adrenoceptor . Yu and Ouyang ( 1997 ) have found that β - adrenoceptor subtypes are unevenly distributed throughout the gastroin - testinal tract , and that β 2 - adrenoceptor is the predominant β - adrenoceptor in the mucosa of rat distal ileum , proximal colon , and distal colon . Roberts et al . "
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    ABSTRACT: Dopamine, an important modulator in the gastrointestinal system, induces concentration-dependent transepithelial ion transport in the distal colon of the rat, as shown by a decrease in the short-circuit current, and acts in a segmentally dependent manner. However, the receptor(s) that mediates dopamine-induced ion transport is unknown. We have investigated the receptor mechanisms underlying dopamine-induced colonic ion transport by means of short-circuit current recording, real-time polymerase chain reaction, and Western blotting analysis, plus gene transfection and enzyme-linked immunosorbance assay. mRNA transcripts of adrenoceptors (alpha, beta) and dopaminergic receptors (D(1) and D(2)) were detected in the rat late distal colonic mucosa, with beta(2) displaying the highest expression. A similar result was found in human colorectal mucosa (equivalent of late distal colon in rat). Pretreatment with a beta(1)-adrenoceptor antagonist (CGP-20712A) and a beta(2)-adrenoceptor antagonist (ICI 118,551) inhibited the dopamine-induced short-circuit current response by 52.59% and 92.51%, respectively. However, neither dopamine D(1) receptor antagonist SCH-23390 nor dopamine D(2) receptor antagonist sulpiride blocked the effect of dopamine. Protein expression of both beta(1)- and beta(2)-adrenoceptors was found in the mucosa of rat distal colon and human sigmoid colon and rectum. Dopamine significantly increased intracellular cAMP levels in COS-7 cells transfected with beta(1)- or beta(2)-adrenoceptors. Thus, beta-adrenoceptors (mainly beta(2)-adrenoceptors), but not dopamine receptors, mediate dopamine-induced ion transport in the late distal colon of the rat. This extends our knowledge of the late distal colon (rats) or colorectum (human) and provides further experimental evidence that might aid the prevention, diagnosis, and clinical therapy of human colorectal diseases.
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    • "Also, because 1-adrenergic receptors were proposed to be located mainly on nerve terminals (Ek et al. 1986), this differential response might result from a difference in enteric innervation. 2-Adrenoceptors have been found to be the prominent type of -adrenergic receptor in the colonic mucosa of the rat (Yu & Ouyang 1997). The 2-agonist terbutaline stimulated PYY release from the isolated colon, although with a lower potency than isoproterenol, as a 10 5 M concentration was required in order to induce a significant secretion. "
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    ABSTRACT: The secretion of PYY by endocrine L cells of the terminal gut is under the control of nutrients, the autonomic nervous system and hormones. Catecholamines, and the non-specific beta-adrenergic agonist isoproterenol induce PYY secretion from rat isolated colon or ileum. Because beta3-adrenergic receptors now appear to mediate many of the effects of catecholamines in the gastrointestinal tract, we investigated the involvement of beta1-, beta2-, and beta3-adrenoceptor stimulation in PYY secretion from the isolated, vascularly perfused rat colon. Infusion of 10(-6) M isoproterenol induced a transient increase in PYY secretion (from 36+/-4 to 87+/-20 fmol/2 min; n=7, P<0.05), that was abolished by a previous infusion of the beta1- and beta2-adrenergic blocker (and partial beta3-agonist) alprenolol (10(-6) M). The beta1-adrenergic agonist dobutamine and the beta-2 agonist terbutaline also (both at 10(-5) M) significantly stimulated PYY secretion, from 29+/-1 to 79+/-12 fmol/2 min and from 19+/-1 to 73+/-13 fmol/2 min respectively (n=7, P<0.05). Neither of the beta3-adrenergic agonists tested (BRL 37 344 (10(-5), 10(-6) M) and SR 58 611A (10(-6) M)) significantly stimulated PYY secretion, thus confirming the exclusive involvement of beta1- and beta2-receptors in beta-adrenergic agonist induced hormone secretion.
    Preview · Article · Feb 2001 · Journal of Endocrinology
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    • "Also, because 1-adrenergic receptors were proposed to be located mainly on nerve terminals (Ek et al. 1986), this differential response might result from a difference in enteric innervation. 2-Adrenoceptors have been found to be the prominent type of -adrenergic receptor in the colonic mucosa of the rat (Yu & Ouyang 1997). The 2-agonist terbutaline stimulated PYY release from the isolated colon, although with a lower potency than isoproterenol, as a 10 5 M concentration was required in order to induce a significant secretion. "

    Preview · Article · Jan 2001 · Journal of Endocrinology
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