Features of the Uncoupling Effect of Fatty Acids in Liver Mitochondria of Mammals with Different Body Weight

V. N. Samartsev^*, L. S. Polishchuk, A. P. Paydyganov, and I. P. Zeldi

Mari State University, pl. Lenina 1, Yoshkar-Ola 421001, Russia; fax: (836-2) 45-4581; E-mail: samartsev@marsu.ru

^* To whom correspondence should be addressed.

Received April 7, 2003; Revision received October 20, 2003

---

In the presence of oligomycin, EGTA, and magnesium ions, the protonophore uncoupling activity of palmitate (V_Pal) is determined as the ratio of the acceleration of respiration with palmitate to its concentration. Under these conditions, V_Pal in liver mitochondria of one-month-old rats with the body weight of 50 g is 1.46-fold higher than in liver mitochondria of adult rats with the body weight of 250 g, whereas the uncoupling activity of FCCP does not depend on the age of the animals. The difference in V_Pal is mainly due to its component insensitive to carboxyatractylate and glutamate (V_Ins). This value is 2.9-fold higher in mitochondria of one-month-old rats than in those of adult rats. The protonophore activity of palmitate is similar in liver mitochondria of four-day-old and adult rats. In liver mitochondria of adult mammals (mouse, rat, guinea pig, rabbit), V_Pal decreases with increase in the body weight of the animals. In double logarithmic coordinates, the dependence of the V_Pal value on the body weight is linear with slope angle tangent of -0.18. The V_Pal value is mainly contributed by its component V_Ins. In the presence of calcium ions, palmitate induces the nonspecific permeability of the inner membrane of liver mitochondria (pore opening). This Ca²⁺-dependent uncoupling effect of palmitate is less pronounced in mitochondria of one-month-old rats than in those of adult rats. In mitochondria of adult animals (mice, rats, and guinea pigs), the Ca²⁺-dependent uncoupling activity of palmitate is virtually the same. It is concluded that the protonophore uncoupling effect of palmitate in liver mitochondria of mammals, unlike its Ca²⁺-dependent effect, is associated with thermogenesis at rest and also with production of additional heat on cooling of the animals.

---

KEY WORDS: liver mitochondria, fatty acids, uncoupling, ADP/ATP antiporter, aspartate/glutamate antiporter, thermogenesis

---