Mast Cell Degranulation, Hepatic Glycogen Depletion, and Hyperglycemia in Compound 48/80 or Pilocarpine–Treated Rats

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Abstract
Blood glucose, hepatic glycogen, and mean carotid blood pressure were determined in anesthetized Sprague–Dawley rats receiving an i.v. infusion of Compound 48/80, pilocarpine, or Ringer's solution as a control. Histochemical determinations of the integrity and number of hepatic mast cells and hepatic glycogen content also were performed at the light microscopic level, and the results compared to those from rats whose livers were treated topically with each of these compounds. Compound 48/80 produced a marked decrease in mean carotid blood pressure, while pilocarpine produced a slight increase in this parameter. Injection of either Compound 48/80 or pilocarpine provoked an increase in blood glucose and a decrease in hepatic glycogen as well as in the number of hepatic mast cells. Infusion produced no change in glycogen within cardiac or skeletal muscle. The application of Compound 48/80 or pilocarpine to the surface of the liver evoked no alteration in the histochemical appearance of hepatic glycogen. However, the topical application of these substances elicited a significant decrease in the number of Falck–Hillarp–positive hepatic mast cells. Blood glucose was higher in rats that survived 30 min or more after injection of either compound. However, glucose levels were significantly higher in rats that survived 30 min or longer following Compound 48/80 infusion than in those surviving pilocarpine treatment. These results provide evidence that the i.v. injection of Compound 48/80 or pilocarpine causes: (a) hyperglycemia; (b) depletion of hepatic glycogen, and (c) a concomitant decrease in the number of Falck–Hillarp–positive mast cells. The degree of hyperglycemia appeared to correlate with the length of survival of the rats and to be independent of the hyper– or hypotensive effects elicited by either chemical.