Somatostatin and lanthanum discriminate two Ca2+ mobilizing mechanisms regulated by bombesin receptors in peptic cells.
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.
Uemura
N
N
Division of Gastroenterology, University of Alabama, Birmingham 35294.
Dickinson
K E
KE
Sekar
M C
MC
Hirschowitz
B I
BI
D000818:Animals; D001839:Bombesin / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004947:Esophagus / Q000187:drug effects / Q000378:metabolism*; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D007811:Lanthanum / Q000494:pharmacology*; D010435:Pepsinogens / Q000037:antagonists & inhibitors / Q000378:metabolism; D011892:Rana catesbeiana; D018004:Receptors, Bombesin; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D013004:Somatostatin / Q000494:pharmacology*
D004338:Drug Combinations; D010435:Pepsinogens; D018004:Receptors, Bombesin; D017981:Receptors, Neurotransmitter; D013004:Somatostatin; D007811:Lanthanum; D001839:Bombesin; D002118:Calcium