Abstract
SUMMARY Slices of rat kidney medulla and cortex were incubated for 30 min in a triglyceride medium with and without heparin; the slices were then removed and Dhe lipolytic activity of the medium measured over the following 30 min. Heparin markedly increased the activity in the medium when medullary slices were used; it had a much smaller effect with cortical preparations. Protamine sulphate and 1 M sodium chloride inhibited the activity released by medullary slices. Homogenates of rat kidney medulla hydrolyzed activated triglyceride to a greater extent than nonactivated substrate. The activity of medullary homogenates was enhanced by heparin and inhibited by protamine and strong salt solutions. Cortical homogenates hydrolyzed activated substrate to only a slightly greater extent than nonactivated substrate, and the activity of these homogenates was not affected by heparin or by protamine sulphate. The results suggest that lipoprotein lipase is present in rat kidney medulla and that a lipase differing from this enzyme in a number of respects is present in rat kidney cortex.
Highlights
Previous studies have shown that heparin augments release of lipoprotein lipase from slices of rat heart, diaphragm, and adipose tissue [3, 5, 6, 7]
In the absence of heparin, the activity found in the medium following incubation of medullary slices was significantly greater than that found with cortical preparations
Heparin increased the activity in the medium when added in the presence of either medullary or cortical slices, this effect wasmuch greater with medullary preparations
Summary
Slices of rat kidney medulla and cortex were incubated for 30 min in a triglyceride medium with and without heparin; the slices were removed and Dhe lipolytic activity of the medium measured over the following 30 min. Homogenates of rat kidney medulla hydrolyzed activated triglyceride to a greater extent than nonactivated substrate. The activity of medullary homogenates was enhanced by heparin and inhibited by protamine and strong salt solutions. Cortical homogenates hydrolyzed activated substrate to only a slightly greater extent than nonactivated substrate, and the activity of these homogenates was not affected by heparin or by protaminesulphate.Theresultssuggest that lipoproteinlipaseispresentin rat kidney medulla and that a lipase differing from this enzyme in a number of respects is present in rat kidney cortex. Earlier observations by Korn suggested that acetonedriedextracts of rat kidneymightcontain lipolyt,ic activity similar to lipoproteinlipase, since these extra& hydrolyzed chylomicron triglyceride to a greater extent thantriglyceride alone ( 2 )
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