A. Bouaziz et al., INFLUENCE OF A CONSTANT OR A MODULATED PRESSURE ON INSULIN-SECRETION BY INTACT MURINE ISLETS OF LANGERHANS - EXISTENCE OF A THRESHOLD EFFECT, Pancreas, 16(1), 1998, pp. 72-79
Pressure effect on cultured islets was investigated to simulate the be
havior of the endocrine pancreas when subjected to an anatomical chang
e in its environment. Insulin secretion from islets seeded on glass wa
s determined by radioimmunoassays after 12-h exposure to constant or s
ine-wave pressure perturbation, al 37 degrees C and pH 7.4, under well
-defined conditions applied through the culture medium. A specially de
vised setup allowed control of the constant component P-o, the amplitu
de A, and the frequency f of the pressure perturbation. Under constant
conditions, three P-o values (760, 760 + 110, 760 + 250 mm Hg) were e
xplored. Under sine-wave conditions, two frequencies (f = 0.2 and 4.33
Hz) were investigated for P-o = 760 + 110 mm Hg and A = 10 mm Hg, as
well as three amplitude values (A = +/-10, +/-50, and +/-110 mm Hg) fo
r P-o = 760 mm Hg and f = 0.2 Hz. Constant pressure inhibits secretion
, by a factor of up to 60%, as well as low frequency (also by similar
to 60%). Low amplitudes enhance secretion (by 41 and 31%), whereas a h
igher amplitude has a marked inhibiting effect (by 70%). In all cases,
no linearity was observed, showing the existence of a threshold press
ure effect. These results suggest that pressure may be an important pa
rameter in certain forms of endocrine pancreatic dysfunctions.