Carnitine Acetyltransferase in Developing Mammals

Abstract

Carnitine acetyltransferase (CAT) activity was determined in mitochondria and microsomes of liver and brown adipose tissue in fetal and postnatal rats, rabbits and guinea pigs. In rat liver and brown adipose tissue, mitochondrial CAT activity increased perinatally. Microsomal CAT activity also increased in brown adipose tissue. In liver, however, a rise was first noted after the 20th postnatal day. The ratio of mitochondrial to microsomal activity was higher in brown fat than liver throughout the period studied. Absolute values for both were always much higher in brown adipose tissue than in liver. Catalase activity (an enzyme localized in the peroxisomes) in rat liver increased after day 20 while in brown adipose tissue it attained a peak at 7 days after birth. At all times, hepatic activity exceeded activity in brown adipose tissue. The ratio on day 30 was 1 (brown adipose tissue) to 25 (liver). In both guinea pigs and rabbits, hepatic mitochondrial CAT activity was 10- to 20-fold higher than in the rat already prenatally. Microsomal activity, on the other hand, was approximately the same in all three species. It is concluded that probably only the mitochondrial CAT is directly related to fatty acid oxidation. The role of microsomal enzyme remains unclear.

Carnitine and Carnitine Transferases in the Intestinal Mucosa of Suckling Rats

“…Mitochondrial carnitine acetyl transferase (CAT) was determined as described previously [7], Carnitine pal mitoyltransferases (CPT) I and II were determined according to HoppeI [11], using either l4C-carnitine or l4C-palmitoylcarnitinc as substrate. The latter was a generous gift from Dr. Hoppe!.…”

“…[5], but not in liver [3]. As the level of carni tine in the milk falls [4], the hepatic rate of synthesis of carnitine from y-butyrobetainc increases [6] so that sufficient carnitine is available throughout the suckling period.Concomitantly with the above changes there is a rise in the activities of the carnitine transferases in liver [7], brown fat [5], and even brain [5] with peak activity usually be ing attained before the start of weaning.One tissue has been more or less ignored in relation to fat metabolism and carnitinethe intestinal mucosa. Considering that car-…”

Metabolic Changes in a Patient of Methylmalonic Aciduria Treated with D, L-Carnitine Supplement

“…D,L-Carnitine drip infusion (50 mg/kg) increased the serum level of free carnitine (to 106.2 nmol/m1). The decrease in serum free fatty acid was suspected to be a result of stimulation of fatty acid oxidation by carnitine infusion [4,25]. A decrease in ketone bodies was also noticeable ( Table 5).…”

Some Aspects of Renal Energy and Lipid Metabolism in Newborn Rats

“…Then no major changes occur [1], Estimating the metabolic activity of cor tex tissue mainly as the activity of the proxi mal tubular cells, the oxygen consumption of these cells might be slightly underestimated in 5-day-old rats as the metabolic rate of glo meruli is low in comparison with tubular cells [14]. Several enzyme activities have been investigated in the kidney during matu ration; most of these activities increase dur ing development [7,19,23,24,27,30,32]. It is not possible to correlate these findings with the data of tissue respiration presented here.…”