Biomedical subjects

A C Garcia-Montero

Publications and source records attributed to A C Garcia-Montero.

8 recordsLinked to original sources

PubMed1999

Selective exocytosis of zymogen granules induces non-parallel secretion in short-term cholecystokinin-stimulated rats.

Parallel studies on pancreatic enzyme secretion and zymogen granule enzyme composition have been carried out in rats subjected to infusion of cholecystokinin (CCK) (1.25 microgram/kg per h) over 30 min. Flow cytometric analysis showed a significant decrease in the mean value of granule size after CCK stimulation. The amount of trypsinogen stored in each individual zymogen granule was significantly lower at 30 min of CCK infusion, but no variation in intragranular amylase content was observed. As a result, the amylase/trypsinogen ratio was significantly increased in the zymogen granules that remained in the pancreas of rats stimulated with CCK for 30 min. A significantly greater proportion of trypsin than amylase was secreted after 30 min CCK infusion. Our results support the existence of different types of granules loaded with different proportions of enzymes. We conclude that short-term CCK stimulation induces the selective release of large granules containing a high proportion of trypsinogen, which leads to a non-parallelism of enzyme secretion.

Amylases↗

PubMed1998

Effect of cholecystokinin blockade on the recovery of alterations induced by acute pancreatitis in glycoconjugates of rat zymogen granules.

Lectin-binding studies have been performed on rat zymogen granules to investigate alterations in the carbohydrate membrane composition that occur in acute pancreatitis induced by caerulein. The influence of treatment with hydrocortisone for seven days before inducing pancreatitis was also studied. Lectin labeling on zymogen granules was also analyzed seven days after inducing pancreatitis in rats that had previously received a hydrocortisone treatment. During this period L 364,718 (0.1 mg/kg)--specific cholecystokinin (CCK) receptor antagonist--was administered daily to some of the rats, and no treatment was applied to others. Using fluorescein-labelled T. purpureus (TP)lectin, a significant decrease in the amount of L-fucose in the granule membrane was observed in rats with caerulein-induced pancreatitis. This effect was directly caused by the pancreatitis and was not influenced by previous hydrocortisone treatment. Seven days later, the density of TP receptors in the granule membrane was similar to the controls both in L-364,718-treated and untreated rats. Therefore, we suggest that endogenous CCK is not an essential factor in the recovery of L-fucose containing glycoconjugates the granule membrane after pancreatitis. Acute pancreatitis did not alter the expression of wheat germ agglutinin (WGA) receptors in the zymogen granule membrane. WGA specifically binds N-acetyl glucosamine and sialic acids. L 364,718 administered for seven days after inducing pancreatitis significantly reduced WGA binding, untreated rats showed a normal zymogen granule membrane. Therefore, the blockade of CCK-induced alterations in membrane glycoconjugates enriched in N-acetyl glucosamine and sialic acid of newly formed granules after pancreatitis, a finding that could explain the delay in the regression of the disease.

Amylases↗

PubMed1997

Hydrocortisone induces an increase of amylase content in individual zymogen granules from rat pancreas.

This study was performed to evaluate the effects of different doses of hydrocortisone (1, 10 and 25 mg/kg/day) administered for 1, 3 and 8 days on pancreatic enzyme storage in rats. The enzyme content in both pancreas homogenates and in individual isolated zymogen granules (ZGs) was measured using standard biochemical assays and flow cytometry, respectively. Hydrocortisone did not alter the total amount of pancreatic DNA but increased the pancreas enzyme content in a time-dose-dependent way. Amylase activity was significantly increased after hydrocortisone administration at day +8 when 10 mg/kg/day was used, and from the first day of treatment when 25 mg/kg/day was administered. A significant increase in trypsin activity was also observed in response to 25 mg/kg/day of hydrocortisone but only from the third day of treatment onwards. As compared with control rats, chronic administration of either 1 or 10 mg/kg/day of hydrocortisone did not alter significantly either the size or the percentage of the two ZG subpopulations (Z1 and Z2) identified in the pancreas by flow cytometry; in addition, no significant changes were observed in the mean amylase content per individual granule, although its mean concentration increased in rats treated with 10 mg/kg/day for 3 and 8 days. Nevertheless, when 25 mg/kg/day of hydrocortisone were administered for 1 and 3 days, a significant increase in the proportion of Z1 ZGs was observed, which may be related to the formation of new and smaller ZGs. When a very high dose of hydrocortisone (25 mg/kg/day) was used, an overall increase in the pancreatic enzyme content related to an increase in the mean amylase content per individual ZG was observed; this effect was apparent from the first day of treatment in the Z1 subset of ZGs and from day +3 in the Z2 subpopulation. Only a high concentration of hydrocortisone was able to alter the enzyme storage process in individual zymogen granules, but they maintain a normal enzyme load at lower hydrocortisone doses.

Amylases↗

PubMed1997

Long-term blockade of cholecystokinin (CCK): effects of L 364,718 (a CCK receptor antagonist) on pancreatic enzyme storage and secretion.

To determine the effect of long-term blockade of cholecystokinin (CCK) on both pancreatic storage and secretion processes, L 364,718 (a CCK receptor antagonist) was administered to rats at 0.1 mg/kg/day for 3, 7, and 15 days. Zymogen granules were analyzed by flow cytometry to determine their light scattering properties-forward scatter and side scatter-as well as their amylase content measured by a specific antiserum. The mean number of zymogen granules per cell was counted on pancreatic sections using electron microscopy. DNA content, pancreatic weight, and enzyme secretion were also studied under both basal conditions and CCK infusion at a dose of 1.25 micrograms/kg/h, which is able to displace the CCK receptor antagonist. Two subpopulations of zymogen granules (Z1 and Z2) were identified on the basis of their light scattering parameters, in both control and L 364,718-treated rats. L 364,718 administered for 3, 7, and 15 days induced a significant reduction in the amylase content of individual zymogen granules, for both Z1 and Z2 zymogen granule subsets. In contrast, the number of zymogen granules per cell increased from day +3 of treatment onward, the highest values being detected at day +7. Hyperplasia was observed only at day +15. Basal enzyme secretion decreased significantly in rats treated with L 364,718 for 3 and 7 days but recovered to control values after 15 days of treatment. No significant differences in CCK-stimulated amylase secretion were observed between control and L 364,718-treated rats. At day +15 of L 364,718 treatment a significant increase in enzyme secretion was observed with respect to shorter treatment periods; this was associated with a significant increase in both the number of cells and the number of zymogen granules per cell. Our results indicate that chronic administration of L 364,718 induces a biphasic effect on pancreatic function. Interestingly, although enzyme secretion reached recovery after long-term treatment (15 days), the storage process is altered since the mean enzyme content in each individual zymogen granule remains significantly reduced.

Amylases↗

PubMed1995

Adrenalectomy induces a decrease in the light scatter properties and amylase content of isolated zymogen granules from rat pancreas as analyzed by flow cytometry.

The effect of glucocorticoid deprivation induced in male rats by adrenalectomy on the pancreatic zymogen granules was studied. Zymogen granules were purified from control, sham-operated and adrenalectomized animals studied 1, 3 and 7 days after surgery. The zymogen granules were characterized by flow cytometry, and in each granule the size (based on the forward or low angle light scatter (FSC) parameter), membrane complexity (based on side or 90 degrees light scatter (SSC) parameter) and amylase content were evaluated. Amylase content/DNA ratio in pancreatic homogenates was also analyzed. The zymogen granules of the control rats were found to be distributed in two populations: a major one-R1 (95.45 +/- 1.21%)-containing zymogen granules with a smaller mean size and complexity, and a minor population-R2 (4.45 +/- 0.24%)-the granules of which had a mean size which was larger and more complex. At day +1 after adrenalectomy the zymogen granules were significantly (P < 0.05) smaller than those of control animals. The R2 zymogen granules were similar to those from R1 as regards their size, but were more complex, suggesting that the immediate effect of glucocorticoid deprivation is to induce a depletion of the larger granules presumably belonging to the R2 population. The amount of amylase per granule did not vary at day +1 after adrenalectomy, although the amylase content/size ratio per granule was significantly (P < 0.001) increased. This mechanism could be explained in terms of the existence of a bypass defined in the adrenalectomized animals between the granular content and cytosolic enzymes. Prolongation of the adrenalectomy period to 3 and 7 days resulted in a progressive increase in zymogen granule size and complexity, both parameters showing similar characteristics to those of the controls at day +7 after adrenalectomy. However, the percentage of zymogen granules within the R1 and R2 populations was clearly different from that of controls since the R2 population was much more numerous (11.25 +/- 0.75% and 15.25 +/- 1.15% (adrenalectomized rats at days +3 and +7 respectively) versus 4.45 +/- 0.24% (controls)). An increase in the content of amylase per DNA was observed in adrenalectomized rats at day +1 although this transient effect cannot be related to glucocorticoid deprivation because it was also observed in sham-operated rats (day +1). However, a significant reduction, nearly 64%, in the amylase content/DNA ratio is produced by the absence of glucocorticoids 7 days after adrenalectomy and this is associated with a reduction in the content of amylase in each individual zymogen granule which reaches a minimum 3 days after adrenalectomy. It should be noted that, despite this, the enzyme concentration in each granule remains constant as there is a parallel decrease in the zymogen granule amylase content and size.

Adrenalectomy↗

PubMed1995

Effects of the cholecystokinin receptor antagonist L-364,718 on pancreatitis induced by a deficient in choline and supplemented with ethionine (CDE) diet in the rat.

The role of cholecystokinin (CCK) in the development of a necrotizing acute pancreatitis induced by a diet deficient in choline and supplemented with ethionine (CDE) has been evaluated in the rat by using a potent CCK receptor antagonist L-364,718. Acute pancreatitis was induced by administration of CDE diet for 14 days. L-364,718 administration was carried out by subcutaneous injections at dose of 0.1 mg/kg/day. Pancreatic exocrine secretion (flow, protein, amylase and trypsin outputs) in resting and under infusion of 1.25 microgram/kg/h of CCK-8 were used to evaluate the pancreatic functionality. Others parameters (serum amylase, percentage fluid in pancreas, haematocrit and mortality) evaluated the severity of pancreatitis. L-364,718 slightly reduced the mortality and the increases of percentage of fluid accumulated in pancreas in CDE diet acute pancreatitis. Basal and CCK stimulated pancreatic secretion was significantly depressed 36 hours after L-364,718 treatment. A slight response to CCK was observed. Nevertheless it was lower than usually observed in control rats. Our results demonstrate that in the rat, chronic L-364,718 treatment did not completely restore pancreatic activity in acute pancreatitis induced by CDE diet. Hence CCK cannot be considered as the main factor involved in the development of this pancreatitis model.

Acute Disease↗

PubMed1994

Therapeutic and protective effect of subcutaneous injections of L-364,718 on caerulein-induced acute pancreatitis.

The prophylactic and therapeutic effects of a potent cholecystokinin (CCK) receptor antagonist, L-364,718, on acute pancreatitis induced by caerulein were evaluated, analyzing morphologic and functional pancreatic parameters jointly. Edematous pancreatitis was induced by four subcutaneous injections of caerulein (20 micrograms/kg) in rats at 1-h intervals. Prophylactic administration of L-364,718 (0.1 mg/kg) prevented rise in serum amylase levels, interstitial edema, vacuolization, and impairment of pancreatic enzyme secretion that accompany caerulein-induced acute pancreatitis. After 7 days, a spontaneous regression of the morphologic alterations caused by caerulein-induced acute pancreatitis occurs; however, recovery of the secretory function of the pancreas was only reached after this period of time when L-364,718 was administered therapeutically (0.1 mg/kg/day). Prophylactically or therapeutically administered, L-364,718 exerts a beneficial effect on caerulein-induced acute pancreatitis, indicating that CCK (exogenous or endogenous) plays an important role in the development of this pathology.

Acute Disease↗

PubMed1994

Acute necrotizing pancreatitis induced by a CDE diet in the rat: a morphologic and functional study.

We studied the effect on the rat pancreas of a choline-deficient diet supplemented with ethionine administered over different time periods. The study was carried out in several groups of male Wistar rats weighing 300 gm and fed for 60, 104, 195, 250, and 336 hours with a choline-deficient diet supplemented with ethionine (CDE). Analysis of pure exocrine pancreatic secretion in animals fed the CDE for 60 hours revealed a decrease in total protein, amylase, and trypsin as compared with animals fed a standard diet. After cholecystokinin stimulation, a gradual decrease in secretion was observed as the duration of the CDE was increased, such that after 336 hours no response to cholecystokinin was found, indicating the lack of pancreatic functionality. Analysis of pancreas preparations by light microscopy showed the existence of infiltration, edema, and hemorrhagic foci after 60 hours of CDE administration. As the duration of the treatment increased, pancreatic morphology deteriorated, with the appearance of vacuolization and foci of necrosis at 195 hours. This deterioration became more pronounced after 250 to 336 hours, progressing to a considerable degree of hemorrhage and necrosis of the acinar tissue. These results clearly confirm the existence of acute necrotizing and hemorrhagic pancreatitis in rats fed a CDE for 250 to 336 hours.

Acute Disease↗