Altered carnitine metabolism in spontaneously hypertensive rats

Carnitine metabolism was examined in spontaneously hypertensive rats (SHR). Carnitine levels were elevated by 25% in hypertrophied hearts of 10- and 15-wk-old SHR when compared with Wistar-Kyoto (WKy) controls. This elevation was associated with a greater than 25% increase in total serum carnitine. The elevated serum carnitine does not appear to be due to increased mobilization from skeletal muscle because carnitine levels were elevated by 25% in gastrocnemius and diaphragm of SHR. Elevated serum carnitine is also not a result of reduced urinary excretion because daily urinary carnitine output was increased by 150% in SHR. These findings suggest that the most likely mechanism for increased serum carnitine is increased carnitine synthesis by the liver. The changes in carnitine metabolism in SHR appear to occur between 5 and 10 wk of age, because the carnitine levels in serum and organs were comparable in 5-wk-old WKy and SHR. The observed alterations in tissue and serum carnitine levels may result in altered fatty acid utilization in SHR.