Male Sprague-Dawley IVA-SIV rats were compared to male Sprague-Dawley Charles River rats of the same age, body weight, and daily food intake. The IVA-SIV rats demonstrated hypertriglyceridemia (182 +/- 9.4 v 131 +/- 9.4 mg/dL, P less than 0.001), associated with increased fasting plasma glucose (115 +/- 3 v 84 +/- 2 mg/dL, P less than 0.001), and plasma insulin (35 +/- 5 v 19 +/- 2 microU/mL, P less than 0.001) levels. Furthermore, IVA-SIV rats responded to an oral glucose load with higher plasma glucose and insulin levels. Very-low-density lipoprotein (VLDL)-triglyceride (TG) turnover studies were performed, documenting a higher TG production rate, which correlated with the plasma TG concentrations, (r = 0.58, P less than 0.01) in the IVA-SIV rats. Since lipoprotein lipase activity in both adipose tissue and muscle was not significantly different in the two groups of rats, it appears that the hypertriglyceridemia in IVA-SIV rats is due to increased VLDL-TG secretion, associated with hyperglycemia, hyperinsulinemia, and increased plasma FFA levels. The IVA-SIV rats provide a model of endogenous hypertriglyceridemia, independent of obesity.