The metabolism of plasma proteins in the young calf

Macdougall, Dugald Francis (1972) The metabolism of plasma proteins in the young calf. PhD thesis, University of Glasgow.

Abstract

The work described in this thesis represents the application of isotopic tracer techniques to a study of the metabolism of the immunoglobulins absorbed from colostrum by the new-born calf. While previous studies, based on serum immunoglobulin levels, have greatly added to our knowledge of this absorption, for precise quantitation it is necessary to know how the immunoglobulins are distributed between the intravascular and extravascular compartments, the rates of equilibration between the compartments and the rates of catabolism, in the neonatal calf. These measurements can only be made satisfactorily using isotopically labelled proteins. Bovine Fast IgG (IgGi) was prepared from neonatal calf serum or colestral whey by a combination of molecular sieve and ion-exchange chromatography, and trace labelled with radio-iodine. The metabolism of IgGi was then studied in Ayrshire calves, less than 1 week old. A distribution of 1.2/1 (Extravascular/Intravascular) was obtained, equilibration being complete by 48 to 72 hours. The occurrence of diarrhoea in some of the calves had a marked effect on the catabolic rates but not on the distribution, although a close correlation was found between the distribution of IgG1 and all four measures of catabolism. The relative size of the extravascular compartment decreased with age. The albumin distribution was found to be 1.91 (Extravascular/Intravascular). Bovine IgM was prepared from colostral whey by molecular sieve chromatography and similarly labelled. In metabolic studies four separate preparations all showed evidence of denaturation and were thus not suitable for providing the information required for absorption studies. Denaturation criteria were investigated. The distribution of two of the preparations indicated that IgM (as in other species) is retained to a greater extent within the circulation, than IgG. Using the information obtained from the metabolic studies, it was then possible to quantitate the efficiency with which the new-born calf absorbs colostral IgG1. Colostrum containing a tracer quantity of 1311 labelled IgG1 was fed by stomach tube to Ayrshire calves, 3 to 6 hours post partum. 48 to 72 hours later, the plasma volume was determined with 1231 labelled IgG1. The total absorbed activity was then calculated and expressed as a % of the activity in the colostrum. IgG levels were also directly measured and the efficiency similarly calculated. When the mean results from both methods were combined, an overall Efficiency of 50% was obtained. The close correlation between the amount of IgG (gm) fed and the amount absorbed indicated a similar efficiency (up to a limit of 250 gm, in 4 litres of colostrum). Information was also obtained about the initial appearance of IgG, in the plasma and its relationship to the proteinuria. A significantly increased leak of macromolecules into the alimentary tract of neonatal diarrhoeic calves was demonstrated with 131I-PVP (40,000 ay. Mol. wt.). This tracer was subsequently - shown to be under-estimating the plasma leak and 51CrC13 was found to be more suitable as a label for quantitative studies. Using 51CrC13, a plasma loss of approximately 50 ml/day was demonstrated in non-diarrhoeic calves which would account for less than half of the Igal. catabolised / day. The investigation of factors influencing the absorption of IgG1 by the new-born calf, is now possible. Similar IgM studies will have to wait until the denaturation problems can be overcome. In addition, a Bovine IgA is now recognised and will require study. It will eventually be possible to investigate the role of all three immunoglobulins in relation to Neonatal Diarrhoea.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: W Mulligan
• Keywords: Animal sciences
• Date of Award: 1972
• Depositing User: Enlighten Team
• Unique ID: glathesis:1972-73256
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jun 2019 08:56
• Last Modified: 14 Jun 2019 08:56
• URI: https://theses.gla.ac.uk/id/eprint/73256