Dietary regulation of glycolytic enzymes X. The effect of oral, intramuscular and conjugated sex steroids on jejunal folate-metabolizing enzyme activities in normal and castrated male and female rats

Abstract

1. 1. The effects of oral, intramuscular and conjugated sex hormones (progesterone, testosterone and estradiol-17β) upon the activities of four enzymes involved in folate metabolism, (glutamate formiminotransferase (N-formimino- L-glutamate:tetrahydrofolate 5-formiminotransferase, EC 2.1.2.5), serine hydroxymethyltransferase ( L-serine : tetrahydrofolate 5,10-hydroxymethyltransferase, EC 2.1.2.1), methylenetetrahydrofolate dehydrogenase (5,10-methylenetetrahydrofolate : NADP oxidoreductase, EC 1.5.1.5) and formyltetrahydrofolate synthetase (formate : tetrahydrofolate ligase (ADP), EC 6.3.4.3)) were studied in the jejunum of normal and castrated male and female rats. 2. 2. These studies demonstrate that oral sex hormones (estradiol in females, testosterone in males) produce significant adaptive increases (P < 0.01) in the activities of jejunal glutamate formiminotransferase, serine hydroxymethyltransferase and methylenetetrahydrofolate dehydrogenase in both normal and castrated rats, while intramuscular sex hormones produced no adaptive increases in the activities of these same enzymes in normal rats. Oral conjugated sex hormones also produce adaptive increases in the activities of serine hydroxymethyltransferase and methylenetetrahydrofolate dehydrogenase in normal rat jejunum.