Date of Award

Spring 1960

Degree Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Klitgaard, Howard M.

Second Advisor

Stekiel, William J.

Abstract

In 1957 Wolff and Ball reported that small amounts of the hormone thyroxine caused the inhibition of malic dehydrogenase. The latter is one of the many enzyme systems in intermediary metabolism which regulates the outflow of hydrogen ions and, in turn, the rate of oxygen consumption. Subsequent reports indicate that this inhibitory action by the thyroid hormones occurs with other DPN-linked dehydrogenating enzymes; that is, those enzymes which remove two electrons from a substrate and pass them on to diphosphopyridine nucleotide, the first link in an electron transport chain. The impact of these discoveries on thyroid physiology lies in the fact that whatever mystery surrounds the mechanism by which thyroid hormones stimulate bodily processes, it is commonly agreed that their action is stimulatory and that these processes are increased in activity due to thyromimetic compounds. The discovery of inhibitory actions by the thyroid hormones poses the following question: Is this inhibitory effect a primary, in vivo biological function of the thyroid hormones and, hence, a key to their mode of activity or is it an invitro side effect of little biological consequence in the normal animal? The main purpose of this thesis is to shed some new light on this question by investigating the activity of one enzyme, malic dehydrogenase, over a period of 28 days after removal of the thyroid gland. Among the numerous members of the physiology department who have contributed to this work, either by congenial discussions, penetrating questions, or those mysterious corridor conversations.

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