Small details between 'in vivo' and 'in vitro' studies make for big differences

Dec 13, 2010

Small details between "in vivo" and "in vitro" studies make for big differences in understanding diabetes and other secretory dysfunctions

Exocytosis, the fundamental process by which cells secrete hormones such as insulin and other useful biological substances, is regulated far differently in life than in laboratory tissue cultures and explanted organs, according to research presented today at the American Society of Cell Biology's 50th Annual Meeting in Philadelphia.

The unexpected findings that exocytosis regulation "in vivo" is not the same as the process long studied "in vitro" is a reminder of the gap between laboratory glassware experiments and the cell biology of living animals -- and humans, said Roberto Weigert, Ph.D., of the National Institutes of Health (NIH), National Institute of Dental and Craniofacial Research (NIDCR).

During exocytosis, a cell internally packs up secretions and ferries them to the plasma membrane (PM) that demarcates the cell from its surroundings.

There, the packages, which are named secretory vesicles, fuse with the PM and then eject their contents. The process has been studied for decades in glassware experiments involving and tissues.

Thanks to the technology intravital microscopy. Weigert and colleagues were able to determine for the first time how exocytosis actually occurs in the salivary glands of a living mouse.

According to previous in vitro studies in the salivary glands, multiple secretory vesicles fuse with the PM, forming strings of vesicles in a process stimulated by two classes of chemical switches, muscarinic and beta-adrenergic receptors.

However, when the scientists examined the process in vivo, they saw the secretory vesicles fuse, not in strings, but one by one with the PM and only under stimulation from beta-adrenergic receptors.

Their additional in vivo studies revealed that the fusion step requires the assembly of a scaffold around the membrane of the vesicles.

This scaffold contains actin, a protein that forms filaments, and myosin II, a protein that binds to multiple actin filaments. When assembled, these molecules generate a contractile force that pushes the membranes and drives the fusion process to completion.

The molecular differences between in vivo and in vitro may seem minor but may have a large impact, said Weigert, because exocytosis is fundamental to understanding the basis of secretory dysfunctions such as diabetes in which insulin is transported in secretory vesicles.

Explore further: Waiting to harvest after a rain enhances food safety

Related Stories

Viewing dye-packed vesicles causes them to explode

Sep 25, 2007

It’s a long-standing question: Can just the act of observing an experiment affect the results? According to a new study by Rockefeller University scientists, if the experiment uses a fluorescent dye called acridine orange, ...

Gene called flower missing link in vesicle uptake in neurons

Sep 03, 2009

As part of the intricate ballet of synaptic transmission from one neuron to the next, tiny vesicles - bubbles containing the chemical neurotransmitters that make information exchange possible -- travel to the tip of neurons ...

Cells use import machinery to export their goods as well

Jul 03, 2009

(PhysOrg.com) -- In the bustling economy of the cell, little bubbles called vesicles serve as container ships, ferrying cargo to and from the port — the cell membrane. Some of these vesicles, called post-Golgi vesicles, ...

A new 'bent' on fusion

Aug 20, 2009

(PhysOrg.com) -- Success in soccer sometimes comes with "bending it like Beckham." Success in cellular fusion -- as occurs at the moment of conception and when nerve cells exchange neurotransmitters -- requires that a membrane ...

Recommended for you

Waiting to harvest after a rain enhances food safety

17 hours ago

To protect consumers from foodborne illness, produce farmers should wait 24 hours after a rain or irrigating their fields to harvest crops, according to new research published in the journal Applied and Environmental Microbiology.

A triangular protein pump

21 hours ago

Ludwig Maximilian University of Munich researchers have elucidated the structure of a molecular machine with an atypical triangular shape that is involved in peroxisome biogenesis, and characterized its conformation ...

Researchers discover new mechanism of DNA repair

Jul 03, 2015

The DNA molecule is chemically unstable giving rise to DNA lesions of different nature. That is why DNA damage detection, signaling and repair, collectively known as the DNA damage response, are needed.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.