Date of Award:

5-1-1977

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Life Sciences:Biology

Committee Chair(s)

James A. Gessaman

Committee

James A. Gessaman

Committee

LeGrande C. Ellis

Abstract

UDPGA fortified rat liver homogenates were incubated with various concentrations of the pineal polypeptide, arginine vasotocin (AVT), and testosterone-4-14C to determine if AVT influenced the rate at which the ∆4-3-ketosteroid molecule was inactivated by the liver. In order to ascertain where in the inactivation mechanism AVT exerts its effect: 1) Mitochondria-free rat liver homogenates fortified with NADPH and various concentrations of AVT were incubated with testosterone as the substrate to determine if AVT influenced ∆4-reductase activity, and 2) rat liver microsomal preparations fortified with UDPGA and various concentrations of AVT were incubated with androsterone-7α-3H as the substrate to determine if AVT directly affects glucuronosyl transferase activity. AVT was shown to effectively inhibit the reduction and subsequent conjugation of testosterone-4-14C by rat liver in vitro in a dose-dependent manner. AVT was demonstrated to significantly inhibit the activity of the ∆4-reductase enzyme in a dose-dependent manner, but failed to significantly influence glucuronosyl transferase activity. The results indicate that AVT can effectively modulate the rate of testosterone inactivation in vitro, and that ∆4-reductase but not glucuronosyl transferase is a target enzyme of AVT. It is proposed that some effects of AVT on gonadal growth and development may be mediated via its effects of ∆4-reductase activity.

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