Relationship between calcium release and potassium release in rat parotid gland.

1. A study was made of the role of Ca release in mediating the sustained phase of K release (86 Rb release) in the rat parotid gland due to receptor activation. 2. Sr could substitute for Ca in supporting the sustained phase of the 86Rb release due to carbachol. Sr was less effective than Ca, while Ba was ineffective. 3. Sr could also restore responsiveness of the transient phase to agonists in media lacking Ca. Again, Sr was less effective than Ca, and Ba was without effect. 4. Carbachol stimulated release of 45Ca from parotid gland slices. The amount of Ca released (about 0.2 micromole/g) was much greater than the estimated Ca influx for the same period. 5. Release of 45Ca by carbachol prevented release due to a subsequent exposure to substance P. 6. Release of 45Ca due to substance P was significantly increased if muscarinic receptors were activated during tissue labelling. 7. These results support an earlier hypothesis whereby different agonists (such as carbachol and substance P) stimulate the release of Ca from a common pool and the release of this Ca mediates the transient phase of the K release response.