Calcium and Calmodulin Antagonists Delay Oral Regeneration in the Ciliate Stentor Coeruleus

The regeneration of a new oral apparatus in Stentor coeruleus (oral regeneration) has been shown to be sensitive to events that inhibit calcium uptake and calmodulin function. Removal of extracellular calcium delays oral regeneration significantly. The calcium channel antagonist verapamil also delays oral regeneration, as does lanthanum, which is known to block calcium uptake. Both inhibitors are active in the concentration range 10~-10~ mol I". Verapamil acts primarily in the earliest stages of regeneration (prior to stage 5) though some minor delays occur in the later stages as well. In addition, verapamil caused an apparent 'clumping' of the pigment granules in the interior of the cell similar to the effects of high concentrations of theophylline and caffeine. The effects of verapamil on oral regeneration were not reversible in the presence of excess extracellular calcium but those of lanthanum were. The calmodulin antagonists trifluoperazine and W-7 were also shown to delay oral regeneration, but the dechlorinated analogue of W-7, W-5, had no effect even at concentrations 10 times those of W-7. The effects of W-7 were not reversed by excess extracellular calcium. These results suggest that calcium uptake is necessary for oral regeneration and that calmodulin is involved in the control and/or formation of the oral apparatus.