Mechanical perturbation of cultured human endothelial cells causes rapid increases of intracellular calcium

Abstract

In first-passage human umbilical vein endothelial cells (HUVEC) and bovine aortic endothelial cells (passages 13-16), exposure to gentle mechanical perturbation using a micropipette caused a transient rise in intracellular calcium concentration ([Ca2+]i). The increase in calcium concentration ([Ca2+]) occurred each time the cell was nudged. Three responses were evoked in each of 27 cells using 5 independent HUVEC harvests. Increase in [Ca2+] returned to near baseline levels within approximately 30 s. The stimulus did not cause membrane puncture, as indicated by 1) absence of rapid dye leakage, 2) regulated nature of the [Ca2+] response, 3) absence of membrane blebbing, and 4) repeatable nature of the response in the same cell. As an alternative stimulus, we created very narrow fluid streams (1- to 2-microns diam) from a pressurized pipette that generated shear stresses of approximately 0.001-0.1 dyn/cm2 on the cells. However, these low-shear streams had little effect on [Ca2+]i. The poke-induced change in [Ca2+] was not blocked by lowering extracellular [Ca2+] ([Ca2+]o; 10 microM). In the absence of [Ca2+]o, however, HUVEC did not respond to the first poke, indicating a requirement for some [Ca2+]o as a mediator of signaling. After several poke-induced responses, [Ca2+]i could still be released by caffeine (100 microM), indicating the integrity of the intracellular release mechanism(s). These studies indicate that the response of an endothelial cell to a membrane-deforming event involves a priming step utilizing [Ca2+]o, which facilitates the transient increase of [Ca2+]i.

Response of descending vasa recta to luminal pressure

“…Most error bars have been suppressed for clarity. microvessels to increase [Ca 2ϩ ] CYT (11,39,41), remodel (2,8,40), modulate permeability (24), and release NO (10,12,13,15) is firmly established. A single predominant mechanism through which endothelia sense and then respond to mechanical forces has not clearly emerged (1,8).…”

Hyperosmotic modulation of the cytosolic calcium concentration in a rat osteoblast‐like cell line.

“…It is known that cell motility changes are generally controlled by [Ca2+]i, which can activate or reverse actin polymerization (Janmey, 1994 Only a few reports demonstrate [Ca2+]i transients in response to a hyperosmotic stimulus, all of them in cardiac cells (Allen & Smith, 1987). There are numerous reports which indicate that a hyperosmotic stimulus inhibits the induction of [Ca2+], transients by other stimuli (Parker & Zhu, 1987;Kazilek, Merkle & Chandler, 1988;Loechner, Knox, Connor & Kaczmarek, 1992 Sigurdson et al 1993), which could be explained in terms of activation of stretch-sensitive channels. This possibility is unlikely in the case of a hyperosmotic stimulus, but cannot be fully excluded, especially in view of the inhibitory action of Gd3+, a common inhibitor of stretch-activated channels.…”

Innexins form two types of channels

“…Intercellular calcium waves are widespread and, in addition to signaling injury to the nervous system, serve important physiological functions, including synchronization of ciliary beats, modulation of synaptic transmission, ossification, and control of vascular perfusion [1][2][3][4]. Calcium waves involve gap junction channels for propagation from cell to cell [1].…”