The dependence of caerulein-evoked pancreatic fluid secretion on the extracellular calcium concentration

Summary

In the perfused rat pancreas fluid and amylase secretion was measured in the absence of stimulation and during stimulation with caerulein or secretin.

Taking away perfusion fluid Ca²⁺ only slightly reduced spontaneous fluid secretion, but caused a marked reduction in the amylase output. In experiments where the CO₂/HCO ⁻₃ -buffer had been replaced by a tris buffer removal of perfusion fluid Ca²⁺ abolished spontaneous fluid and amylase secretion.

Taking away perfusion fluid Ca²⁺ during continuous stimulation with caerulein caused an immediate rapid reduction in fluid and amylase secretion which was reversible upon readmission of Ca²⁺.

Removal of perfusion fluid Ca²⁺ and addition of EGTA during stimulation with secretin had no effect on fluid secretion for the first half an hour after start of Ca²⁺ deprivation. Thereafter a gradual reduction in fluid flow occurred which was non-reversible upon Ca²⁺ readmission.

During stimulation with monobutyryl cyclic AMP Ca²⁺-deprivation failed to reduce fluid secretion within a period of half an hour.

Augmenting the perfusion fluid [Ca²⁺] to 20 mM during stimulation with caerulein caused a sharp reduction in fluid secretion and a small decrease in amylase output. These effects were partially reversible if the period of exposure to the high Ca²⁺ solution was less than 20 min.

It is concluded that extracellular Ca²⁺ is important for caerulein-evoked but not for secretin-evoked fluid secretion.