칼슘, 란타늄, 망간 이온이 토끼 유두근 완만내향전류 및 수축에 미치는 영향

Abstract

The effects of Ca++, La+++ and )\'In++ on the elecmuscletrical and mechanical responses of papillary muscle partially depolarized by 27 mM K十were studied in rabbits. 1. When resting membrane potential of partially depolarized papillary muscle was set at • 40 to -45 mY. therewere no electrical and mechanical activities, after 10μM histamine addition , however , they reappeared. 2. After addition of histamine, Ca++ increased the amplitude of action potential, ψmax (maximum rate of depolarization, (dY/dt)max) and magnitude of contraction. the duration of action potential, however , was shortened. 3. La+++ in concentration of 10-100 I'M decreased the amplitude of action potential from control value of 77±1. 0 mY to 49±1. 0 mY (Mean±S.E.) , Vmu and magnitude of contraction up to 21. 9±3. 1% and 38. 3±2. 4% of control respectively. The duration of action potential was shortened from 245±18.3 msec of control to 150±14.7msec. 4. Mn++(30-300pM) decreased the amplitude of action potential from 75±1. 3 mY to 59. 7±0. 9 mY, Vmo. and magnitude of contraction up to 61. 4±1O. 9 % and 75. 7±3. 0% of control , but lengthened the duration slightly 5. The above results suggest that the amplitude of action potential and ψm o. of partially depolarizcd papillary muscle are a measure of calcium-dependent slow inward current or calcium conductance. gCa.