Development of methods for analyzing plasma lipoprotein concentrations and associated enzyme activities and their use to measure the effects of pregnancy and lactation in cats.
Methods available for measurement of plasma lipoprotein-cholesterol concentrations and activities of lipoprotein lipase, hepatic lipase, lecithin:cholesterol acyl transferase (LCAT), and cholesteryl ester transfer protein were adapted for use in cats. A combined ultracentrifugation/precipitation procedure was used to isolate very low-density lipoproteins (VLDL), then to separate low-density lipoproteins (LDL) from high-density lipoproteins (HDL). The reagent used, 92 mM heparin-manganese chloride, provided complete precipitation of LDL with only trace and insignificant contamination by HDL. Efforts to selectively measure lipoprotein lipase activity in plasma, collected after IV injection of heparin, by inhibiting hepatic lipase with sodium dodecyl sulfate were unsuccessful, and the activity of this enzyme was calculated as the difference between total and hepatic lipase activities. The latter was measured in the presence of high salt concentration to inhibit lipoprotein lipase. Cholesterol esterifying activity was identified in feline plasma and was typical of LCAT, in that it was dependent on apolipoprotein A-I as a cofactor. The intra-assay and interassay coefficients of variation for measurement of lipoprotein lipase, hepatic lipase, and LCAT activities were 18.4, 4.6, and 7.2%, and 20.4, 10.7, and 5.3%, respectively. Appreciable cholesteryl ester transfer protein activity was not detected in either undiluted or diluted plasma. These methods were subsequently used to investigate the effects of pregnancy and lactation on lipoprotein metabolism in a group of 10 queens. Plasma concentrations of cholesterol and triglycerides were unaltered during pregnancy, but the concentrations of VLDL-cholesterol increased and those of HDL-cholesterol decreased.(ABSTRACT TRUNCATED AT 250 WORDS)
Watson
T D
TD
Department of Pathological Biochemistry, Royal Infirmary, University of Glasgow, United Kingdom.
Butterwick
R F
RF
McConnell
M
M
Markwell
P J
PJ
D000818:Animals; D001774:Blood Chemical Analysis / Q000379:methods / Q000662:veterinary; D002265:Carboxylic Ester Hydrolases / Q000097:blood*; D002415:Cats / Q000097:blood*; D005260:Female; D007774:Lactation / Q000097:blood*; D008049:Lipase / Q000097:blood; D008071:Lipoprotein Lipase / Q000097:blood; D008074:Lipoproteins / Q000097:blood*; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000097:blood*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000097:blood*
D008074:Lipoproteins; D007862:Phosphatidylcholine-Sterol O-Acyltransferase; D002265:Carboxylic Ester Hydrolases; D008049:Lipase; D008071:Lipoprotein Lipase