Dynamics of Ca2+ transients in norepinephrine-stimulated individual H-35 hepatoma cells: fura-2 digital imaging microscopy and high time-resolution microspectrofluorometry.

Abstract

We investigated spatiotemporal changes in cytoplasmic free Ca2 concentration ([Ca2 Jj) in norepinephrine (NE)-stimulated and fura-2-loaded individual H-35 rat hepatoma cells, using digital imaging microscopy and high time-resolution microspectrofluorometry. Application of NE (5 x 10 M) resulted in an initial transient increase in [Ca2 jj, followed by a small sustained [Ca2 Ji plateau above the pre-stimulaiion level. The initial peak and the small sustained plateau originated from intracellular stores and the extracellular space, respectively. The initial transient evoked by NE was totally blocked by phentolamine, an a-adrenergic antagonist, but was not blocked by either pre-incubation with nominally Ca2-free medium or by pre-treatment ofcells with La3. On the other hand, the sustained plateau was eliminated by act synergistically (2,7,29).

Ca2+ Dynamics in Rat Pancreatic AR-42J and AR-IP Cells.

“…This result suggested that AR-42J has a a-adrenergic receptor. Recently, we have reported that rat hepatoma cell line, H-35, has a aadrenergic receptor (23). It is interesting to point out here that AR-42J cells contain a-adrenergic receptor, because no norepinephrine action to pancreatic exocrine acinar cell has been reported so far as we know.…”

“…Weused a digital imaging microscopy system for Ca2+mesure-ment, which is composedof inverted microscope IMT-2RFL with a color image analyzer, CIA-102 (OLYMPUS, Japan) and equipped with an OSP-2 microspectrofluorometer as described previously (21). The system was improved by changing the light source from a mercury lamp to a 75Wxenon lamp (23). Emission wavelength was 510 nm, while the excitation wavelength was 340 nm/380 nm.…”