Yagi H, Snape W J, Hyman P E
Department of Pediatrics, Harbor-UCLA Medical Center, Torrance.
Gastroenterology. 1991 Apr;100(4):980-5. doi: 10.1016/0016-5085(91)90273-n.
Bombesin and its mammalian homologue, gastrin-releasing peptide, stimulate smooth muscle contraction and may promote the growth of gastrointestinal tissues. Isometric contraction of strips from circular muscle of the gastric fundus and longitudinal muscle of the distal colon were used to compare changes in the response to bombesin in newborn and weanling rabbits. There was an age-related qualitative change in gastric muscle from biphasic contractions including phasic and tonic components in the newborn to phasic contractions alone in the weanling. The colon contractions were tonic at both ages. In both tissues there was an age-related fivefold increase in stress in response to maximally effective concentrations of bethanechol (P less than 0.05). In contrast, in the stomach age-related decreases in the response to maximally effective concentrations of bombesin were observed, from 2930 +/- 179 mN/cm2 (98% of the maximal response to bethanechol) in the newborn to 565 +/- 81 mN/cm2 (4% of the maximal response to bethanechol) in the weanling (P less than 0.005). In the colon, a twofold increase in response to bombesin was observed, from 446 +/- 59 mN/cm2 (82% of the response to bethanechol) in the newborn to 862 +/- 11 mN/cm2 (29% of the response to bethanechol) in the weanling (P less than 0.05). No age-related changes were observed in the potency of bombesin in either tissue. Neither atropine nor tetrodotoxin altered the contractions in either tissue, suggesting that bombesin interacted directly with myocytes. There was three times as much bombesinlike immunoreactivity in the stomach compared with the colon, but no age-related changes in either tissue. In summary, by the age of weanling the stomach lost the tonic component of contraction and 80% of the efficacy of bombesin-stimulated phasic contraction that had been present in the newborn. The loss of efficacy, absolute in the stomach and relative to bethanechol in the colon, suggest that bombesin may be most important in stimulating motility in the neonatal period.
蛙皮素及其哺乳动物同源物胃泌素释放肽可刺激平滑肌收缩，并可能促进胃肠道组织生长。采用胃底环行肌条和远端结肠纵行肌条的等长收缩来比较新生兔和断奶幼兔对蛙皮素反应的变化。胃肌存在与年龄相关的质的变化，从新生兔的双相收缩（包括相性和紧张性成分）到断奶幼兔的单相相性收缩。两个年龄段的结肠收缩均为紧张性收缩。在两种组织中，对最大有效浓度的氨甲酰甲胆碱的反应强度均有与年龄相关的五倍增加（P<0.05）。相比之下，在胃中观察到对最大有效浓度蛙皮素的反应随年龄增长而降低，从新生兔的2930±179 mN/cm²（对氨甲酰甲胆碱最大反应的98%）降至断奶幼兔的565±81 mN/cm²（对氨甲酰甲胆碱最大反应的4%）（P<0.005）。在结肠中，观察到对蛙皮素的反应增加了两倍，从新生兔的446±59 mN/cm²（对氨甲酰甲胆碱反应的82%）增至断奶幼兔的862±11 mN/cm²（对氨甲酰甲胆碱反应的29%）（P<0.05）。在两种组织中均未观察到蛙皮素效力与年龄相关的变化。阿托品和河豚毒素均未改变两种组织中的收缩，提示蛙皮素直接与肌细胞相互作用。胃中的蛙皮素样免疫反应性是结肠的三倍，但两种组织中均未观察到与年龄相关的变化。总之，到断奶时，胃失去了收缩的紧张性成分以及新生兔中存在的蛙皮素刺激的相性收缩效力的80%。效力的丧失，在胃中是绝对的，在结肠中相对于氨甲酰甲胆碱是相对的，这表明蛙皮素在刺激新生儿期的运动中可能最为重要。
