| The Effect of Erythromycin on Gastric Antrum and Low Esophageal Sphincter in the Newborn Rabbit |
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Sung Dong Choi, Chung Sik Chun |
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Department of Pediatrics, College of M edicine, The Catholic University, Seoul, Korea |
| 신생가토에서 Erythromycin의 위 전정부 및 식도 하부괄약근에 대한 효과 |
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최성동, 전정식 |
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가톨릭대학교 의과대학 소아과학교실 |
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| Abstract |
Purpose
: We studied smooth muscle strips from rabbit gastric antrum and low esophageal
sphincter(LES) to explore the difference between newborn and adult rabbit on erythromycin(EM)-
induced contractions. Another aim of this study was to determine the mechanism of LES contractile
activities induced by erythromycin(EM).
Methods
: Muscle strips prepared from newborn and adult rabbits were stimulated with agonists
such as KCl, motilin and EM, and the isometric tensions were measured. To study the underlying
mechanism of EM-stimulated contraction of LES, the receptor antagonsts, including tetrodotoxin,
hexamethonium, atropine, propranolol and phentholamine, were used. A high concentration of
motilin(1μM) was employed to provoke tachyphylaxis.
Results
: Antral smooth muscle and LES from newborn rabbits developed less active force than
those from adult rabbits when stimulated with KCl, motilin and erythromycin, however, the effective
concentrations(EC50s) were similar in both age groups. Antral smooth muscle strips showed
both tonic and phasic contractions but LES muscle strips showed only tonic contractions. These
findings were observed in both newborn and adult rabbits. The contraction force of antral smooth
muscle strips in response to agonists was greater than that of LES. The contractile response of
LES to repeated motilin or EM administration was markedly decreased. EM- induced contractions
of LES were markedly decreased by motilin tachyphylaxis but were unaffected by tetrodotoxin,
hexamethonium, atropine or propranolol plus phentolamine.
Conclusion
: The data suggest that the contractilities of antrum and LES smooth muscle from
newborn rabbit are less than those from adult ones, however, the effective concentratons of
EM(EC50) are not different between the two age groups. The results also suggest that erythromycin
induces the contraction of rabbit LES via motilin receptor in vitro. |
| Key Words:
Erythromycin, Motilin, Gastrointestinal motility, Newborn rabbit |
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