D-600 sensitive and insensitive spontaneous contractions in the guinea-pig hepatic duct.
The mechanical properties of the longitudinally cut preparations of the guinea-pig hepatic duct were studied. About 42% of the preparations (18 of 43 preparations) showed spontaneous phasic contractions which were unaffected by either tetrodotoxin, guanethidine or atropine. About 60% of them exhibited phasic contractions which appeared at irregular frequencies in the same tissue and varied in size. This sort of contractions usually accompanied small contractions. In about 20%, contractions occurred constantly in frequency (about 6-14 every 10 min) and in size. The remaining 20% showed twitch-like contractions which occurred sporadically. These contractions were classified into two types depending upon the susceptibility to the Ca2+ entry blocker, D-600. D-600 (1-100 microM) strongly suppressed both regularly occurring contractions and twitch-like ones. On the other hand, the drug was ineffective on irregularly occurring contractions. The Ca2+ sources underlying these contractions were discussed.
Suzuki
H
H
Third Department of Internal Medicine, Tohoku University School of Medicine, Sendai.
Fukushi
Y
Y
Wakui
M
M
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D005711:Gallopamil / Q000494:pharmacology*; D006168:Guinea Pigs; D006500:Hepatic Duct, Common / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*
D002121:Calcium Channel Blockers; D005711:Gallopamil