Substance measured

Abstract

It has been shown previously (Zor, Dikstein & Sulman, 1965a, b) that the mono-amine oxidase inhibitor mebanazine inhibits the release of somatotrophin (STH). This could be demonstrated in rats by the marked decrease in the width of the epi-physial cartilage and by showing that the release of corticotrophin (ACTH), the natural antagonist of STH, was stimulated. This effect is greatly potentiated by corticosteroids. The aim of the present study was to investigate to which of the enzyme systems involved in growth the ability of mebanazine to inhibit growth is related. Immature male rats of the 'Sabra ' strain of the Hebrew University, 5 weeks old, weighing 60 \m=+-\5 g., received i.p. injections of mebanazine resinate (which contains only 35 % of the base), 30 mg./kg./24 hr., for 20 days (six injections weekly). They were killed on the day after the last injection. DNA was separated from RNA by the method of Schneider (1957), and was then assayed according to Ceriotti (1955). Protein was assayed as described by Lowry, Roseborough, Farr & Randall (1951). Table 1. Effects of mebanazine resínate (30 mg.¡kg.¡24, hr. for 20 days, six i.p. injec¬ tions weekly) on the activity of growth-conditioning enzymic systems in the liver of growing male rats (means ± s.E.) Five rats per group