Plasma amylin concentrations in fasted and fed rats quantified by a monoclonal immunoenzymometric assay.

Amylin is a 37-amino acid peptide co-secreted from the pancreatic beta-cell with insulin in response to nutrient stimuli. Plasma amylin concentrations in the rat are reported to vary widely. We have employed a recently-developed immunoenzymometric assay to quantify plasma amylin concentrations in fasted, fed and glucose-administered rats. Fasted amylin concentrations ranged between 1.02+/-0.09 and 1.63+/-0.15pM among three different common rat strains, and increased up to 7.70+/-0.80 pM after feeding. The differences among strains and between fasted and fed rats were all significant at P<0.01 or less. Intravenous glucose administration (5.2 mmol/kg) also significantly increased plasma amylin concentrations in fasted rats from 1.5+/-0.3pM to 3.4+/-0.5pM, and in fed rats from 4.6+/-1.1 pM to 9.1+/-1.7 pM. Plasma amylin/insulin molar ratios ranged between 2.3+/-0.2% and 3.6+/-0.5% (mean 3.0%), but did not differ among strains, or between the fasted vs fed state in any strain. In conclusion, a new sensitive immunoenzymometric assay revealed fasting plasma concentrations which are lower than previously reported, and which are significantly increased by stimulation with feeding or glucose administration.