Modification of excitation-contraction coupling in cat ventricular myocardium following endocardial damage.

Damage to endocardial endothelium (denudation of the superficial tissue) by brief exposure to a 100-microL bolus of detergent (Triton X-100, 1% by volume stock) decreased the twitch force of papillary muscle (and trabeculae) by approximately 30% to a new but steady level without changes in resting tension. The decline in twitch force was evident immediately after the addition of Triton. Modification of the action potential measured from the contracting tissue appeared only later, when the change in contraction was already well established (i.

Changes in prejunctional potency of B-HT 933 during aging in the rat vas deferens.

1. Age-related changes in prejunctional alpha 2-adrenoceptors were examined in the rat vas deferens using pharmacological techniques. 2.

Formation of the primitive myo- and endocardial tubes in the chicken embryo.

The morphogenesis of the mesenchymal cardiogenic plate, the formation of the bilateral heart primordia leading to the primitive heart tube, and also the genesis of the endocardial tube, have been studied in 1 to 13 somite chick embryos. The morphological data were compared with those obtained in electrophysiological studies of the development of the cardiac action potentials (Fujii et al., 1981a).

Calcium channels and excitation-contraction coupling in cardiac cells. II. A pharmacological study of the biphasic contraction in guinea-pig papillary muscle.

Biphasic contractions were obtained in guinea-pig papillary muscle by inducing partial depolarization in K+-rich solution (17 mM) in the presence of 0.3 microM isoproterenol. Mn2+ ions inhibited the two components of contraction in a similar way.

Calcium channels and excitation-contraction coupling in cardiac cells. I. Two components of contraction in guinea-pig papillary muscle.

Biphasic contractions have been obtained in guinea-pig papillary muscle by inducing partial depolarization in K+-rich solution (17 mM) containing 0.3 microM isoproterenol; whereas in guinea-pig atria, the same conditions led to monophasic contractions corresponding to the first component of contraction in papillary muscle. The relationships between the amplitude of the two components of the biphasic contraction and the resting membrane potential were sigmoidal curves.