Page E, Upshaw-Earley J, Goings G E, Hanck D A
Department of Medicine, University of Chicago, Illinois 60637.
Am J Physiol. 1993 Oct;265(4 Pt 1):C986-96. doi: 10.1152/ajpcell.1993.265.4.C986.
Fluid-phase endocytosis (FPE) associated with recycling of fused plasmalemma-secretory granules or membranes and/or membrane receptors by in situ cardiac myocytes was studied at 37 degrees C in vitro noncontracting adult rat atrial preparations. Measurements included 1) the volume (VS*) of the compartment consisting of presumptive endocytotic vesicles and the endosomes or lysosomes transiently in continuity with them (S*), which internalizes [14C]-sucrose but is inaccessible to simultaneously measured [methoxy-3H]inulin, 2) the kinetics of [14C]sucrose efflux from S*, and 3) morphometry to quantify interstitial space and non-heart muscle cells. Vs* (0.39 +/- 0.04 ml/g dry atrium for unstretched atria at 37 degrees C) was 1) variable over a 3.7-fold range under various experimental conditions, 2) significantly increased by neomycin or by lowering the temperature to 18 degrees C, and 3) significantly decreased by alpha 1-adrenergic stimulation. Analysis of sucrose efflux kinetics confirmed the presence of an intramyocytic sucrose-containing compartment. A smaller inulin-inaccessible sucrose space (S*) was also present in right ventricle. Thus, during FPE, vesicles and endosomes initially containing high (extracellular) Ca2+ and Cl- concentrations continually enter, circulate within, and undergo exocytosis from myocardial cells.
在37℃下，利用体外非收缩成年大鼠心房制备物，研究了与融合的质膜 - 分泌颗粒或膜以及/或膜受体循环相关的液相内吞作用（FPE）。测量内容包括：1）由推测的内吞小泡和与之短暂连续的内体或溶酶体组成的区室（S*）的体积（VS*），该区域内化[14C] - 蔗糖，但对同时测量的[甲氧基 - 3H]菊粉不可接近；2）[14C]蔗糖从S流出的动力学；3）形态计量学以量化细胞间隙和非心肌细胞。VS（37℃下未拉伸心房的干重为0.39±0.04 ml/g心房）在各种实验条件下有以下特点：1）在3.7倍的范围内变化；2）新霉素或将温度降至18℃可使其显著增加；3）α1 - 肾上腺素能刺激可使其显著降低。蔗糖流出动力学分析证实了心肌细胞内存在含蔗糖的区室。右心室中也存在较小的对菊粉不可接近的蔗糖空间（S*）。因此，在FPE过程中，最初含有高（细胞外）Ca2+和Cl-浓度的小泡和内体持续进入心肌细胞、在细胞内循环并经历胞吐作用。
