Lipolytic Activity of Renal Cortex during Ontogenetic Development in Rats

Abstract

The lipolytic activity of rat kidney cortex was investigated in newborn and adult rats. Two peaks of lipolytic activity could be detected at pH 5.0 and 8.4, respectively. Lipase activity at pH 5.0 is completely inhibited by 0.2 M sodium fluoride and can be stimulated by norepinephrine (10 μg/ml). Full activity is already present in 5-day-old rats. The response to sodium fluoride and norepinephrine is identical in newborn and adult animals. Lipase activity at pH 8.4 is inhibited up to 85% by 0.6 M sodium chloride. Activity is very low in 5-day-old rats and increases during maturation. This lipase can be stimulated by heparin (100 μg/ml) by about 10–25% in newborn and adult animals.

In vivo and in vitro microdialysis sampling of free fatty acids

“…This particular problem has previously been observed by others. When performing microdialysis of lipophilic substances Groth and co-workers observed that the recovery of sodium fusidate increased with increasing concentrations, probably due to interaction between the membrane and sodium fusidate [13]. However, in our hands the addition of 0.25% BSA to the perfusion fluid resulted in a concentration independent recovery, indicating that some sort of binding took place without added BSA.…”

“…Following 70 min of baseline sampling, an intraperitoneal injection (1 mg/kg) of the specific ␤ 3 -adrenerg agonist, BRL37344, was given at time 0 min, in order to stimulate lipolysis. Plasma samples were taken at time: −70, −10, 10, 70, 110 and 150 min in EDTA-coated tubes containing NaF to prevent lipolysis during storage [13]. After termination of the experiment the probe was carefully removed and the rat was decapitated.…”