Enhancement of noradrenaline-induced salivary flow and chromogranin A secretion in vascularly perfused submandibular gland isolated from the inbred heat-tolerant FOK rat

Previous study has provided evidence that chromogranin A-like immunoreactiv ity (CgA-like IR) is stored in the exocrine cells in the granular convolute d tubles (GCT), and is secreted highly concentrated CgA-like IR (less than or equal to 0.4 mM) into saliva in response to noradrenaline (NAd; 1-100 mu M) in the perfused submandibular gland isolated from male Wistar rat. The present study shows that, in the perfused gland isolated from the inbred he at-tolerant FOK rat, the combined stimulation with NAd (1-100 mu M) and 0.1 mu M acetylcholine increased salivary secretion containing highly concentr ated CgA-like IR: the 100 mu M NAd-induced salivary flow rate and CgA-like IR release rate in the FOK rats did not decreased but remained at higher le vels almost identical to the corresponding levels induced by 10 mu M NAd, a nd these secretory responses were significantly larger than the correspondi ng responses in the control rats. Possible mechanisms involved in the maint ained secretory responses to 100 mu M NAd were discussed in conjunction wit h the heat and cold tolerance of salivary glands in FOK rat.