Alterations of the pancreatic secretory responses to secretin and to the ionophore A23187 by reserpine: a calcium-mediated phenomenon?

This study was undertaken to further characterize the secretory response of the rat pancreas after reserpine treatment. Rats were given reserpine (1 mg kg-1 day-1 i.p.) or vehicle for 7 days. To distinguish between specific effects of reserpine and those related to secondary malnutrition caused by the drug, the secretory response of a group of pair-fed (PF) animals to reserpine was also investigated. Amylase release from dispersed pancreatic acini, prepared from control (C), PF and reserpine-treated (R) rats were used to evaluate functional secretory capacity. Reserpine and pair-feeding caused reduced responses of pancreatic acini to secretin. The pair-feeding-altered secretin response was greatly improved by increasing extracellular Ca2+ concentration, whereas a slight improvement was noticed in the R group. Reserpine significantly reduced the secretory response to the ionophore A23187 at concentrations above 5 x 10(-7) M in 1.25 mM Ca2+; in 2.5 mM Ca2+, the response to the ionophore was significantly higher in the R group than in C at all ionophore concentrations. Furthermore, at 2 x 10(-7) M ionophore, the secretory response to secretin in the R group became significantly higher than that in the C group but comparable to that of the control+ionophore. In conclusion, reserpine affects the secretory response to secretin as did pre-exposure of pancreatic acini to a high concentration of carbamylcholine. The modified secretory response to the ionophore following reserpine treatment indicates that reserpine may act as a 'Ca2+ entry mechanism' antagonist which may explain the partial reduction in the secretin response.

Long-term exercise training with constant energy intake. 2: Effect on glucose metabolism and resting energy expenditure.

The effect of exercise training on glucose and insulin metabolism as well as on resting energy expenditure was investigated in five young men (mean BMI = 27.5 +/- 2.9 (s.d)). Subjects performed cycle-ergometer exercise 6 days/week over a 100 day period and the quantity of daily exercise was calculated to induce a 4.2 MJ/day surplus in energy expenditure during the days of training. As expected, significant weight and fat losses were observed in response to the training program. Exercise training induced a significant reduction in fasting levels and in the responses of insulin to a 4.2 MJ meal or an oral glucose load. Most of the training effects were noted after only 25 days of training. However, a significant decrease in plasma C-peptide concentrations during the oral glucose tolerance test was observed only at the end of the exercise program whereas essentially no change occurred during the first 25 days of training. The resting metabolic rate (RMR) and the thermic effect of food (TEF) were not significantly modified by training. Results show that the reduction in plasma insulin induced by training occurred earlier than that for C-peptide. Moreover, the absence of change in RMR in the presence of a substantial weight loss may represent a beneficial effect of training in comparison to the documented effect of diet-induced weight loss on RMR.