Animals

Ninety-seven virgin male Sprague-Dawley rats at 12 weeks old (200 - 250 g) were given standard rat chow and water ad libitum. After an overnight fast, we induced type I diabetes by a single IP injection of 55 mg/kg of STZ (Sigma-Aldrich Inc.) in 100 mM citrate buffer (pH 4.5); an equivalent volume of 100 mM citrate buffer (pH 4.5) was used in control animals as a sham injection. Seventy-seven rats were injected with STZ and 20 rats were used as control. Of all STZ-injected rats, 22 developed diabetes and 26 developed diabetic gastroparesis. Twenty-nine STZ-injected rats died, did not develop diabetes, or underwent diabetes reversal. Five control rats were chosen randomly for the control group. The five animals with the highest fasting blood glucose levels and the five animals with the slowest measurement of gastric emptying were chosen for the diabetic and diabetic gastroparesis groups, respectively. Blood glucose was measured after overnight fasting every third day for 16 weeks using an Accu-check blood glucose meter (Roche Diagnostics, Basel, Switzerland). A blood glucose level of > 300 mg/dL was considered diabetic. At 12 weeks, we subjected rats to a gastric emptying assay. This test allowed us to split the rats into the following study groups: male rats: 1) control citrate buffer injection (CM); 2) diabetic after STZ treatment (DM); and 3) diabetic and gastroparetic after STZ treatment (DM + GP). At the end of week 16, serum and gastric tissues were collected from the animals for biochemical assays.