Effect of cholinergic drugs on calcium movement in guinea pig taenia coli.

Abstract

The effect of cholinergic drugs on Ca movement was investigated in guinea pig taenia coli. In the presence of carbachol (1 × 10 -6 M), Ca content and extracellular space did not differ from control value, 45 Ca uptake and efflux increased in the “early phase” and the size of cellular Ca fraction which did not exchange within 4 min (tightly bound fraction, TBF) increased in the “late phase” in the contraction. When the muscle was pretreated with atropine (1 × 10 -6 M), carbachol did not induce the contraction and 45 Ca uptake and efflux in the “early phase” and the size of TBF in the “late phase” was maintained at the control value. The effect of pilocarpine (5 × 10 -6 M) and acetylcholine (1 × 10 -5 M) on Ca movement was the same with carbachol. In summary, cholinergic drugs increase Ca exchange and continuously accumulate the cytoplasmic Ca ions into the slow exchanging fraction. Changes in Ca movement by various stimulants were classified into three types, 1, increase in Ca exchange, 2, increase in Ca net influx and subsequent accumulation and 3, release of cellular Ca and subsequent accumulation.