Tap generation in isolated pancreatic acini under bombesin stimulation

Pancreatic exocrine function of a new inbred strain Otsuka Long-Evans Tokushima Fatty (OLETF) rat that develops spontaneous persistent hyperglycemia was evaluated in in vitro isolated pancreatic acini and compared with that in the control Long-Evans Tokushima Otsuka (LETO) rat. Serum glucose and insulin concentrations in the OLETF rats were significantly high (glucose: 270 +/- 12 vs. 208 +/- 10 mg/100 ml, P < 0.01; insulin: 12.4 +/- 1.7 vs. 4.9 +/- 0.6 ng/ml, P) < 0.01), whereas pancreatic wet weight was significantly low (803 +/- 20 vs. 1,138 +/- 17 mg, P < 0.01) compared with those in the LETO rat. Pancreatic acini isolated from the OLETF rat were totally insensitive to cholecystokinin (CCK)-8 stimulation at concentrations of up to 100 nM. However, neither the responsiveness nor the sensitivity to carbamylcholine, bombesin, and secretin of the acini from the OLETF rat was altered or even increased, probably due to the larger amylase content in the OLETF rat acini compared with those of the LETO rat acini (31.5 +/- 2.0 vs. 13.0 +/- 1.1 Somogyi units/micrograms DNA, P < 0.01). The responsiveness to fluoride, a direct activator of guanine nucleotide-binding protein, in the OLETF rat acini was similar to that in the LETO rat, suggesting that the transmembrane signaling and effectors and subsequent intracellular signal transduction molecules in the OLETF rat acini are normal. Moreover, 125I-CCK binding to the acini prepared from the OLETF rat was totally absent. These present results indicate that the OLETF rat has a selective defect in the binding of CCK to its receptors on the acinar cell surface.

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Amylase secretion by isolated pancreatic acini after acute cholecystokinin treatment in vivo

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1984.246.4.g419 ◽

1984 ◽

Vol 246 (4) ◽

pp. G419-G425 ◽

Cited By ~ 1

Author(s):

M. Otsuki ◽

Y. Okabayashi ◽

A. Ohki ◽

S. R. Hootman ◽

S. Baba ◽

...

Keyword(s):

Binding Sites ◽

Amylase Secretion ◽

Response Curves ◽

Amylase Release ◽

Pancreatic Acini ◽

Cholecystokinin Receptor ◽

Isolated Pancreatic Acini ◽

And Control ◽

Quinuclidinyl Benzilate

A single dose of synthetic cholecystokinin octapeptide (CCK8, 5 micrograms/kg) in a depot carrier was injected subcutaneously into rats 2 and 14 h before the removal of the pancreas and the preparation of isolated pancreatic acini. CCK8 treatment induced no significant change in body weight or total amount of pancreatic DNA, but pancreatic weight, total pancreatic protein and amylase, and the concentration of amylase and total protein relative to DNA were significantly decreased. In acini prepared from CCK8-pretreated rats, responsiveness to maximal and supramaximal concentrations of CCK8 was significantly increased, irrespective of whether the amount of amylase released was expressed relative to DNA or calculated as a percentage of the acinar content. The dose-response curves for CCK8 were similarly shaped in both CCK8-pretreated and control rats but shifted threefold toward higher concentrations of CCK8 2 or 14 h after CCK8 treatment. Specific 125I-CCK binding was significantly increased only for high-affinity binding sites. Although these observations suggest that alterations in pancreatic amylase release could be due to changes at the cholecystokinin receptor, the secretory responsiveness to maximal and supramaximal concentrations of carbachol was also increased without any change in the sensitivity. Moreover, in contrast to the cholecystokinin receptor, there was no change in the number of muscarinic receptors or in their affinity for either agonists or antagonists measured with [3H]quinuclidinyl benzilate.(ABSTRACT TRUNCATED AT 250 WORDS)

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