Quantitation of somatostatin inhibition of insulin-stimulated gastric acid and pepsin secretion in the cat

Somatostatin inhibition of gastric acid and pepsin secretion stimulated by insulin-hypoglycaemia was quantified in six conscious cats prepared with cannulated gastric fistulae. Somatostatin 0.5-5μg kg ^-1 h ^-1 produced a dose dependent reduction of both acid and pepsin secretions stimulated by insulin 0.2 u kg ^-1 h ^-1. The doses of somatostatin which produced 50% inhibition of pepsin and acid secretions (ID ₅₀) were not significntly different (0.70 ± 0.16 and 0.93 ± 0.11 μg kg ^-1h ^-1 respectively). The slope of the calculated correlation line relating % inhibition of pepsin and % inhibition of acid is within experimental error of unity indicating equality of action of somatostatin on insulin-stimulated acid and pepsin secretion. The results indicate that somatostatin is a more potent inhibitior of insulin 0.2 μ kg ^-1h ^-1 stimulated acid secretion than pentagastrin 8μg kg ^-1 h ^-1 stimulated acid secretion, but is a more potent inhibitor of pentagastrin insulin - stimulated pepsin secretion. As insulin stimulates less acid and more pepsin secretion than pentagastrin, the differences in sensitivities to somatostatin of these secretions produced by the two stimulants is thought to be a result of the different absolute amounts of secretion produced by the stimulants.