MECHANISM OF HYPERTRIGLYCERIDEMIA IN DAHL RATS

Plasma triglyceride concentrations were shown to be higher in hypertensive (153+/-2 mm Hg) male Dahl salt-sensitive rats than in control Sprague-Dawley rats (122+/-2 mm Hg). These differences in triglyceride concentrations were seen when blood was drawn at 9 AM from unfasted animals (229+/-27 versus 111+/-8 mg/dL), at 1 PM after k 4-hour fast (186+/-13 versus 88+/-4 mg/dL), or at 9 AM after a 13-hour fast (151+/-6 versus 90+/-6 mg/dL), all p<0.001. Total triglyceride secretion was also compared in groups of rats by determining the increment in plasma triglyceride concentration for 2 hours after blocking triglyceride removal from plasma by injecting Triton. Studies performed at 1 PM and 9 AM, after the 4- and 13-hour fast, demonstrated that total triglyceride secretion was greater (p<0.05) in Dahl rats only when studied at 1 PM. Direct estimates of hepatic triglyceride secretion at 1 PM also demonstrated a significant (p<0.02) increase in secretion rate by perfused livers from Dahl rats, due in part to their increased liver size. In addition, removal of prelabeled very low density lipoprotein-triglyceride in the intact rat was significantly (p<0.05) decreased in Dahl rats. Lipoprotein lipase activity measured in skeletal muscle, heart, and adipose tissue was also significantly decreased at 9 AM and 1 PM (after 0 and 4 hours of fasting) in tissue from Dahl rats. These data confirm that Dahl rats have higher plasma triglyceride concentrations than Sprague-Dawley rats. Since both total and hepatic triglyceride secretion were somewhat greater in Dahl rats, in association with a decrease in both removal of very low density lipoprotein from plasma and decreased muscle and adipose tissue lipoprotein lipase activity, it seems likely that hypertriglyceridemia in Dahl rats results from a combination of increased triglyceride secretion and decreased triglyceride removal.