Ultrastructural morphometric investigation of peroxisome development in piglets during the first 4 weeks of lifeThe number of hepatic peroxisomes, cores, marginal plates, and microperoxisomes in piglets increases from a low level at birth, compared with other species e. g. the rat, to day 28 of life. The number of peroxisomes is correlated to the activity of uricase, but morphometry alone is not sufficient to quantitate uricase activity. These findings might explain the occurence of renal uric acid deposition (infarction) during a catabolic state, where body protein is metabolized to an increased extent and purine levels rise. Due to a relative lack of uricase uric acid is not completely oxidised to allantoin.
Summary
Liver and kidney peroxisomes in dogs fed a purin‐rich or purin deficient diet. An ultrastructural‐morphometric study
Number and structural components (cores and marginal plates) of liver and kidney peroxisomes were compared morphometrically in dalmatian and beagle dogs fed purin‐rich (single cell protein) and purin deficient (casein) diets.
The major difference was that dalmatians, independently of wether on a purin‐rich or a purin‐poor diet, had more and larger peroxisomes than beagles.
This is interpreted as an adaptation mechanism with each type of diet when there is a raised uric acid level. For the uricase, morphologically identified as core in peroxisomes, there were no differences attributable to breed or feeding. This fits in with biochemical determinations of uricase activity and the demonstration that the extensive inability of dalmatians to oxidize uric acid to allantoin is not a lack of uricase but rather the lack of a specifically efficient transport of uric acid into liver cells.
Zusammenfassung
Es wurden die Struktur und Anzahl der Peroxisomen (“marginal plates” und “cores”) in der Leber von Dalmatinern und Beagles untersucht. Geprüft wurde der Einfluß einer purinreichen (Single Cell Protein) und einer purinarmen (Kasein) Diät.
Der wesentliche Unterschied besteht darin, daß Dalmatiner unabhängig von einer purinreichen bzw. ‐armen Fütterung mehr und größere Peroxisomen aufweisen als Beagles. Dies wird als Anpassungsmechanismus an einen, auch bei purinarmer Fütterung, erhöhten Harnsäurespiegel gedeutet. Für die sich morphologisch als “core” in Peroxisomen darstellende Uricase fanden sich keine wesentlichen rasse‐ oder fütterungsabhängigen Unterschiede. Dies deckt sich mit biochemischen Bestimmungen der Uricaseaktivität und dem Nachweis, daß die weitgehende Unfähigkeit von Dalmatinern, Harnsäure in Allantoin zu oxidieren, nicht auf einem Mangel an Uricase beruht, sondern auf dem Fehlen eines spezifisch wirksamen Transports von Harnsäure in die Leberzellen.
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