| Summary: | Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item. Includes bibliographical references (leaves 50-56). Issued also on microfiche from Lange Micrographics. Pinnipeds (seals and sea lions) have an elevated mitochondrial volume density [Vv(mt)] and citrate synthase (CS) and β-hydroxyacyl-CoA dehydrogenase (HOAD) activity in their swimming muscles, to maintain aerobic metabolism, as an adaptation for diving hypoxia. However, little is known about the aerobic capacity of other organs, such as the heart, kidneys, and splanchnic organs. The goal of this study was to determine if any of these organs have an elevated Vv(mt) and CS and HOAD activity as an adaptation for sustaining aerobic metabolism and normal function during hypoxia. Samples of heart, liver, kidney, stomach, and small intestine were taken from ten freshly dead harbor seals (Phoca vitulina) and fixed in glutaraldehyde for transmission electron microscopy or frozen in liquid nitrogen for enzymatic analysis. Samples from dogs and rats were used for comparative purposes. Mitochondrial volume density per volume of tissue scaled to mass specific metabolic rate in the heart, liver, kidneys, stomach and small intestine of harbor seals was elevated when compared to that of terrestrial control animals such as dog and rat. The Vv(mt)/RMR (RMR = mass specific resting metabolic rate) of the harbor seal heart was 1.4 and 2.3X greater than the dog and rat, respectively. Vv(mt)/RMR of the harbor seal liver was 2.5 and 5X greater than the dog and rat, respectively. Vv(mt)/RMR of the harbor seal kidney was 2 and 4X greater than the dog and rat, respectively. The Vv(mt)/RMR of the harbor seal stomach was 1.8 and 4.5X greater than the dog and rat, respectively. The Vv(mt)/RMR of the harbor seal intestine was 3 and 3.3X greater than the dog and rat, respectively. CS ...
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