The Journal of Nutrition Vol. 127 No. 5 May 1997, pp. 753-757
Copyright ©1997 by the American Society for Nutritional Sciences

Desaturation of Stearate Is Insufficient to Increase the Concentrations of Oleate in Cultured Rat Hepatocytes

Manuscript received 25 September 1996. Initial reviews completed 15 November 1996. Revision accepted 21 January 1997.

Nutrition Department, The Pennsylvania State University, University Park, PA 16802

Desaturation of stearate and palmitate and its effect on cellular accumulation of oleate were determined in primary culture of rat hepatocytes. The rate of oleate synthesis as measured by the formation of monounsaturated fatty acids from stearate was significantly higher than that from palmitate. The rate of [1-¹⁴C]stearate incorporation into oleate [1208 ± 195 pmol/(mg protein·4 h)] was 80% higher than that of [1-¹⁴C]palmitate [(672 ± 82 pmol/(mg protein·4 h)]. Despite the different rates of desaturation, the cellular oleate concentrations did not differ in the cells treated with stearate and palmitate (i.e., 42.5 ± 4.5 vs. 40.8 ± 5.2 nmol/mg protein). On the other hand, oleate concentration in the cells incubated with exogenous oleate was 198.1 ± 9.5 nmol/mg protein. There was a dose-dependent increase in cellular stearate concentration by increasing stearate concentrations from 0.5 mmol/L to 4.0 mmol/L in culture medium. A linear increase in cellular stearate concentration was also achieved by increasing the duration of incubation with 1.0 mmol/L stearate from 2 to 24 h. Despite the marked increases in stearate concentrations under these conditions, oleate concentrations remained unchanged in the cells. These results do not support the contention that the hypocholesterolemic effect of stearate may be mediated by its conversion to oleate, although stearate is a more favorable substrate for desaturation than palmitate.