The Effect of an Extracellular Mucilage on the Response to Osmotic Shock in the Charophyte Alga Lamprothamnium papulosum

The Effect of an Extracellular Mucilage on the Response to Osmotic Shock in the Charophyte Alga... We have used current/voltage (I/V) analysis to investigate the role played by extracellular mucilage in the cellular response to osmotic shock in Lamprothamnium papulosum. Cells lacking extracellular mucilage originated in a brackish environment (1/3 seawater). These were compared, first with cells coated with thick (∼50 μm) extracellular mucilage, collected from a marine lake, and second, with equivalent mucilaginous marine cells, treated with heparinase enzyme to disrupt the mucilage layer. Histochemical stains Toluidine Blue and Alcian Blue at low pH identified the major component of the extracellular mucilage as sulfated polysaccharides. Treating mucilage with heparinase removed the capacity for staining with cationic dyes at low pH, although the mucilage was not removed, and remained as a substantial unstirred layer. Cells lacking mucilage responded to hypotonic shock with depolarization (by ∼95 mV), cessation of cyclosis, due to transient opening of Ca2+ channels, and opening of Ca2+-activated Cl− channels and K+ channels. Cell conductance transiently increased tenfold, but after 60 min was restored to the conductance prior to hypotonic shock. Mucilaginous cells depolarized by a small amount (∼18 mV), but Ca2+ channels failed to open in large enough numbers for cyclosis to cease. Likewise most Ca2+-activated Cl− channels failed to open and conductance increased only ∼1.2-fold above the prehypotonic level. After 60 min conductance was less than the conductance prior to hypotonic shock. Heparinased mucilaginous cells recovered several aspects of the hypotonic response in cells lacking mucilage. These cells depolarized (by ∼103 mV); cyclosis ceased, indicating that Ca2+ channels had opened, and conductance increased to ∼4 times the value prior to hypotonic shock, indicating that Ca2+-activated Cl− channels opened. However, after 60 min, these cells had neither restored membrane potential (and remained at positive values), nor decreased their conductance. It was not possible to determine whether K+ channels had opened. The heparinased cells recovered the normal hypotonic response of mucilaginous cells when heparinase was washed out. Apical seawater cells, which lacked mucilage, were unaffected by heparinase treatment. The results demonstrate that the presence of extracellular sulfated polysaccharide mucilage impacts upon the electrophysiology of the response to osmotic shock in Lamprothamnium cells. The role of such sulfated mucilages in marine algae and animal cells is compared and discussed. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png The Journal of Membrane Biology Springer Journals

The Effect of an Extracellular Mucilage on the Response to Osmotic Shock in the Charophyte Alga Lamprothamnium papulosum

Loading next page...
 
/lp/springer_journal/the-effect-of-an-extracellular-mucilage-on-the-response-to-osmotic-koXdhvJwFI
Publisher
Springer-Verlag
Copyright
Copyright © Inc. by 1999 Springer-Verlag New York
Subject
Life Sciences; Biochemistry, general; Human Physiology
ISSN
0022-2631
eISSN
1432-1424
D.O.I.
10.1007/s002329900552
Publisher site
See Article on Publisher Site

Abstract

We have used current/voltage (I/V) analysis to investigate the role played by extracellular mucilage in the cellular response to osmotic shock in Lamprothamnium papulosum. Cells lacking extracellular mucilage originated in a brackish environment (1/3 seawater). These were compared, first with cells coated with thick (∼50 μm) extracellular mucilage, collected from a marine lake, and second, with equivalent mucilaginous marine cells, treated with heparinase enzyme to disrupt the mucilage layer. Histochemical stains Toluidine Blue and Alcian Blue at low pH identified the major component of the extracellular mucilage as sulfated polysaccharides. Treating mucilage with heparinase removed the capacity for staining with cationic dyes at low pH, although the mucilage was not removed, and remained as a substantial unstirred layer. Cells lacking mucilage responded to hypotonic shock with depolarization (by ∼95 mV), cessation of cyclosis, due to transient opening of Ca2+ channels, and opening of Ca2+-activated Cl− channels and K+ channels. Cell conductance transiently increased tenfold, but after 60 min was restored to the conductance prior to hypotonic shock. Mucilaginous cells depolarized by a small amount (∼18 mV), but Ca2+ channels failed to open in large enough numbers for cyclosis to cease. Likewise most Ca2+-activated Cl− channels failed to open and conductance increased only ∼1.2-fold above the prehypotonic level. After 60 min conductance was less than the conductance prior to hypotonic shock. Heparinased mucilaginous cells recovered several aspects of the hypotonic response in cells lacking mucilage. These cells depolarized (by ∼103 mV); cyclosis ceased, indicating that Ca2+ channels had opened, and conductance increased to ∼4 times the value prior to hypotonic shock, indicating that Ca2+-activated Cl− channels opened. However, after 60 min, these cells had neither restored membrane potential (and remained at positive values), nor decreased their conductance. It was not possible to determine whether K+ channels had opened. The heparinased cells recovered the normal hypotonic response of mucilaginous cells when heparinase was washed out. Apical seawater cells, which lacked mucilage, were unaffected by heparinase treatment. The results demonstrate that the presence of extracellular sulfated polysaccharide mucilage impacts upon the electrophysiology of the response to osmotic shock in Lamprothamnium cells. The role of such sulfated mucilages in marine algae and animal cells is compared and discussed.

Journal

The Journal of Membrane BiologySpringer Journals

Published: Aug 1, 1999

There are no references for this article.

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off