Deprecated: Implicit conversion from float 211.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 211.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 211.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 211.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 211.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 211.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 211.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Deprecated: Implicit conversion from float 211.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534
Warning: imagejpeg(C:\Inetpub\vhosts\kidney.de\httpdocs\phplern\7328118
.jpg): Failed to open stream: No such file or directory in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 117 J+Cell+Biol
1981 ; 91
(3 Pt 1
): 716-27
Nephropedia Template TP
gab.com Text
Twit Text FOAVip
Twit Text #
English Wikipedia
Exocytosis of pinocytosed fluid in cultured cells: kinetic evidence for rapid
turnover and compartmentation
#MMPMID7328118
Besterman JM
; Airhart JA
; Woodworth RC
; Low RB
J Cell Biol
1981[Dec]; 91
(3 Pt 1
): 716-27
PMID7328118
show ga
The uptake and fate of pinocytosed fluid were investigated in monolayers of
pulmonary alveolar macrophages and fetal lung fibroblasts using the fluid-phase
marker, [14C]sucrose. Initial experiments revealed that cellular accumulation of
chromatographically repurified [14C]sucrose was not linear with incubation time.
Deviation from linearity was shown to be due to constant exocytosis of
accumulating marker. Chromatographic analysis revealed that the cells were unable
to metabolize sucrose and were releasing it intact by a process that was
temperature-sensitive but not dependent on extracellular calcium and magnesium. A
detailed analysis of the kinetics of exocytosis was undertaken by preloading
cells with [14C]sucrose for various lengths of time and then monitoring the
appearance of radioactivity into isotope-free medium. Results indicated that
modeling the process of fluid-phase pinocytosis and subsequent exocytosis
required at least two intracellular compartments in series, one compartment being
of small size and turning over very rapidly (t1/2 = 5 min in macrophages, 6--8
min in fibroblasts) and the other compartment being apparently larger in size and
turning over very slowly (t1/2 = 180 min in macrophages, 430--620 min in
fibroblasts). Computer-simulation based on this model confirmed that the kinetics
of efflux faithfully reflected the kinetics of influx and that the rate of efflux
completely accounted for the deviation from linearity of accumulation kinetics.
Moreover, the sizes of the compartments and magnitude of the intercompartment
fluxes were such that the majority of fluid internalized in pinocytic vesicles
was rapidly returned to the extracellular space via exocytosis. This result
provides direct experimental evidence for a process previously thought necessary
based solely on morphological and theoretical considerations. Furthermore, the
turnover of pinocytosed fluid was so dynamic that accumulation deviated from
linearity even within the first few minutes of incubation. We were able to show
that the kinetics of exocytosis allowed calculation of the actual pinocytic rate,
a rate that was nearly 50% greater than the apparent initial rate obtained from
the slope of the uptake curve over the first 10 min.
free
free
free
