We analyzed [Ca2+] i transients in Paramecium cells in response to veratridine for which we had previously established an agonist effect for trichocyst exocytosis (Erxleben & Plattner, 1994. J. Cell Biol. 127:935–945; Plattner et al., 1994. J. Membrane Biol. 158:197–208). Wild-type cells (7S), nondischarge strain nd9–28°C and trichocyst-free strain ``trichless'' (tl), respectively, displayed similar, though somewhat diverging time course and plateau values of [Ca2+] i transients with moderate [Ca2+] o in the culture/assay fluid (50 μm or 1 mm). In 7S cells which are representative for a normal reaction, at [Ca2+] o = 30 nm (c.f. [Ca2+] rest i =∼50 to 100 nm), veratridine produced only a small cortical [Ca2+] i transient. This increased in size and spatial distribution at [Ca2+] o = 50 μm of 1 mm. Interestingly with unusually high yet nontoxic [Ca2+] o = 10 mm, [Ca2+] i transients were much delayed and also reduced, as is trichocyst exocytosis. We interpret our results as follows. (i) With [Ca2+] o = 30 nm, the restricted residual response observed is due to Ca2+ mobilization from subplasmalemmal stores. (ii) With moderate [Ca2+] o = 50 μm to 1 mm, the established membrane labilizing effect of veratridine may activate not only subplasmalemmal stores but also Ca2+ o influx from the medium via so far unidentified (anteriorly enriched) channels. Visibility of these phenomena is best in tl cells, where free docking sites allow for rapid Ca2+ spread, and least in 7S cells, whose perfectly assembled docking sites may ``consume'' a large part of the [Ca2+] i increase. (iii) With unusually high [Ca2+] o , mobilization of cortical stores and/or Ca2+ o influx may be impeded by the known membrane stabilizing effect of Ca2+ o counteracting the labilizing/channel activating effect of veratridine. (iv) We show these effects to be reversible, and, hence, not to be toxic side-effects, as confirmed by retention of injected calcein.
The Journal of Membrane Biology – Springer Journals
Published: Jun 1, 1999
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
Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly
Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.
Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.
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.
“Hi guys, I cannot tell you how much I love this resource. Incredible. I really believe you've hit the nail on the head with this site in regards to solving the research-purchase issue.”Daniel C.
“Whoa! It’s like Spotify but for academic articles.”@Phil_Robichaud
“I must say, @deepdyve is a fabulous solution to the independent researcher's problem of #access to #information.”@deepthiw
“My last article couldn't be possible without the platform @deepdyve that makes journal papers cheaper.”@JoseServera