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The effects of cadmium on the responses to the agonists, K, acetylcholine, noradrenaline, Ba and Ca were investigated in the isolated vas deferens from guinea pig. 1. The low concentration of cadmium enhanced the effects of tested agonists, and the enhancement was larger in order of K, Ba, Ca, noradrenaline=acetylcholine. 2. The high concentration of cadmium inhibited the effects of tested agonists with a dose-dependent manner. The inhibitory effect was weaker against the contraction by K and was stronger against the contractions by Ba, Ca, acetylcholine and noradrenaline. 3. The inhibitory effects of cadmium against the contractions by acetylcholine and noradrenaline were almost the same. 4. On the shape of contraction by K, cadmium showed the stronger inhibition against the tonic contraction than the phasic contraction. 5. The above mentioned results were mainly discussed on the Ca mobilization and the receptor selectivity.

In the guinea-pig ileal longitudinal smooth muscle, Ba caused an initial phasic contraction, followed by a gradual decrease of the contraction (tonic contraction). In the Ca-free and the Ca-free, K-rich physiological solution, Ba could also contract the longitudinal muscle, but 30 min- and 60 min-immersion of the tissue in the Ca-free solution decreased lower than 20% of control of the Ba contraction. Although the K-induced depolarization intensified the Ba contraction after the 30 min-immersion, within 10 min after the immersion in the two solutions there is no difference in the height of Ba contractions. In the normal physiological solution, Ba seems to serve the contractile protein with free Ca ions rather than itself for the Ba contraction. D-600 induced an equal inhibition on the Ba contractions in the normal physiological solution and in the Ca-free solution, and it inhibited the tonic contraction more than the phasic one. The phasic component may be due to the cellular Ca mobilized by Ba which passes through D-600-sensitive pathway, and at least part of the tonic component may utilize the extracellular Ca. Benactyzine perferentially inhibited the Ba contraction in the Ca-free solution, and it depressed the phasic component more than the tonic one. Treatment with papaverine induced an equal inhibition on the phasic and tonic components of Ba contractions and the Ba contraction in the Ca-free solution. Benactyzine may exert the main influence on the mobilization of the cellular Ca through the competition with Ca. Papaverine seems to inhibit the Ba contractions by diverse actions.

By using the isolated seminal vesicles of guinea pigs, the effects of dibutyryl cyclic AMP and beta-stimulant, orciprenaline, on the responses to Ca, K, acetylcholine and Ba were investigated, especially in relation to cyclic AMP. The following results were obtained. 1. Orciprenaline inhibited the contraction produced by Ca, K, acetylcholine and Ba in a dose-dependent manner, and the inhibition became larger in the order of Ca, K, acetylcholine and Ba. 2. Dibutyryl cyclic AMP showed the same results as those of orciprenaline. That is, dibutyryl cyclic AMP inhibited the contractions produced by acetylcholine and Ba. 3. Orciprenaline showed the increased level of cyclic AMP in a dose-dependent manner. But the increase was not remarkable in the concentration in which the contractions produced by the tested contractile agents were inhibited by about 50%. From these results, the following suggestions were obtained; (1) there exists beta-receptor in guinea pig seminal vesicles and (2) a part of actions of orciprenaline is due to a mechanism unrelated to cyclic AMP.