Somatostatin and lanthanum discriminate two Ca2+ mobilizing mechanisms regulated by bombesin receptors in peptic cells |
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Authors: | N Uemura K E Dickinson M C Sekar B I Hirschowitz |
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Institution: | Division of Gastroenterology, University of Alabama, Birmingham 35294. |
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Abstract: | Bombesin (BB)-stimulated pepsinogen secretion from frog esophageal peptic acini was inhibited 40% by somatostatin (SS) (IC50 = 1 nM), and by 30-50% by low concentrations (10(-7)-10(-4)M) of lanthanum chloride. SS inhibited basal secretion as well as both early (0-2 min) and late (2-30 min) BB-stimulated secretory phases. By contrast, LaCl3 selectively inhibited the late secretory phase and was without effect on basal secretion. SS (100 nM) and LaCl3 (30 microM) attenuated BB-stimulated 45Ca2+ uptake, and the combination resulted in additive inhibition. High K+ media decreased basal secretion, abolished SS but not LaCl3 inhibition of BB-stimulated secretion, and blocked SS inhibition of BB-mediated 45Ca2+ uptake. These findings suggest the existence on peptic cells of distinct La3+-sensitive, and somatostatin-sensitive, K+ dependent, Ca2+ mobilizing mechanisms which contribute to BB receptor-mediated secretion. |
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