| Budget Amount *help |
¥6,900,000 (Direct Cost: ¥6,900,000)
Fiscal Year 1986: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1985: ¥6,000,000 (Direct Cost: ¥6,000,000)
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| Research Abstract |
Species and regional differences in the response of isolated smooth muscle to vasodilator drugs were examined using isolated rabbit and rat aortae and guinea pig taenia coli. Comparing the contractions induced by either high concentrations of K and receptor agonists in these smooth muscle, it was found that (1) addition of receptor agonists to the muscle maximally activated by high K elicited additional contraction, and (2) in the muscle treated with high K, but not by receptor agonists, Sr and Ba ions entered the cell to elicit contraction. These results suggest the existence of two distinctive Ca channels in these smooth muscles, voltage-dependent channel (VDC) which is activated by membrane depolarization and passes Ca, Sr and Ba, and receptor-linked channel (RLC) which is activated by receptor agonists and passes only Ca. In the next series of experiments, effects of vasodilators on these Ca channels were examined. Ca channel blockers and facilitators relatively selectively modulated the VDC in rabbit aorta although both of the channels were relatively nonselectively affected in rat aorta and guinea pig taenia. In contrast to this, nitro-compounds relatively selectively inhibited RLC in rabbit aorta, relatively nonselectively in rat aorta and had showed little effect in the taenia. The aorta isolated from newborn rabbit showed similar characteristics as those in rat aorta and gradually changed with age. These results suggest the existence of species, regional and age-related changes in the sensitivity of Ca channels to vasodilators in smooth muscle.
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