Table of Contents
How is intrinsic clearance measured?
Determination of in vitro intrinsic clearance For the hepatocyte assay, CLIN VITRO, INT (ml/h/106 cells) was determined by dividing k by the measured concentration of viable cells.
What is microsomal protein?
Microsomes are artificial structures derived from pieces of endoplasmic reticulum (ER) formed during tissue homogenization. They are prepared by differential centrifugation at 10,000 and 100,000 × g and contain cytochrome P450 enzymes (CYPs), but do not contain soluble enzymes.
What are the microsomal enzymes?
There are several microsomal enzymes, including flavin monooxygenases, cytochrome P450, NADPH cytochrome c reductase, UDP Glucoronosyl transferases (UGT), glutathione-S-transferases, epoxide hydrolases, etc. Cytochrome P450 and NADPH cytochrome c reductase are the two main enzymes in this system.
What is a liver microsome?
Liver microsomes are subcellular fractions which contain membrane bound drug metabolizing enzymes. Microsomes can be used to determine the in vitro intrinsic clearance of a compound. The use of species-specific microsomes can be used to enable an understanding of interspecies differences in drug metabolism.
What is a rough Microsome?
Rough microsomes (RMs) are small vesicular fragments of the rough endoplasmic reticulum (ER). They can be used in cell-free protein translocation studies to analyze ER targeting signals, signal sequence cleavage, N-linked glycosylation, and membrane protein biogenesis.
How do you calculate unbound intrinsic clearance?
Since only unbound drug is available to metabolizing enzymes, the measured CLint becomes a function of the microsomal or hepatocyte concentration, related to the unbound metabolic intrinsic clearance (CLint,u): CLint = fuinc × CLint,u.
What is a high intrinsic clearance?
With a high intrinsic clearance, the hepatic metabolism is highly effective at removing the drug from the circulation. Increased blood flow will increase the delivery of the substrate to the enzyme system, and the enzyme system will cope admirably.
What is a smooth Microsome?
Smooth microsomes accumulate somewhat higher amounts of Ca2+ than rough ones in the presence of MgATP. In the presence of glucose 6-phosphate, which markedly stimulates MgATP-dependent Ca2+ accumulation in both fractions, smooth microsomes exhibit a much higher Ca2+-accumulating capacity than rough ones.
What are microsomal fractions?
a collection of tiny subcellular particles, invisible with the light MICROSCOPE, that are produced during DIFFERENTIAL CENTRIFUGATION of eukaryotic cells. Under the ELECTRON MICROSCOPE, these microsomes can be seen to consist mainly of membranes and RIBOSOMES from the ENDOPLASMIC reticulum.