Conversion of Norepinephrine to Epinephrine in Canine Testes 1

Abstract

In 1968 Eliasson and Risley 1 reported on levels of the catecholamines, norepinephrine, and epinephrine in the testis, epididymis, and vas deferens of the cat, rabbit, guinea pig, and rat. Recently, Eik-Nes 2 observed that when isoproterenol, epinephrine, or norepinephrine was administered via the spermatic artery of the dog, secretion and production of testosterone increased. Norepinephrine was a weaker stimulant than epinephrine and exhibited its maximal effect on testosterone secretion at a slower rate than epinephrine. This difference may possibly reflect a gradual conversion of norepinephrine to epinephrine in the dog testis. The enzyme phenethanolamine N-methyl transferase catalyzes the conversion of norepinephrine to epinephrine 3 , but its presence in vertebrate testes has not been reported. Axelrod and Goldzieher 4 demonstrated, however, that human testes contain transmethylation activity as shown by the conversion of 2-hydroxy steroids to their 2-methoxy analogs.

The purpose of this communication is to show that canine testes convert norepinephrine to epinephrine in vivo.

Experimental Procedure. Testes were infused via the spermatic arteries as described by our laboratories 2 . The constant flow of arterial blood in this preparation (animal preparation no. 2, see Ref. 2) was 3.86 ml per min. Tritiated norepinephrine (DL-norepinephrine-7-³H, specific activity 5 Ci/mmole, obtained from New England Nuclear) was dissolved in 0.9% sodium chloride solution and added to the arterial blood in the spermatic artery at a constant rate of 0.38 ml/min. When used, human chorionic gonadotropin, (HCG, obtained from Ayerst Laboratories) was added to the 0.9% sodium chloride solution containing tritiated norepinephrine.

Spermatic venous blood from infused testes was collected in 15-min samples over the 90-min infusion period and centrifuged at 1000g for 30 min. Plasma fractions were adjusted to 0.4 N with 4 N perchloric acid and refrigerated for 18 hr. Infused testes were weighed and homogenized (Waring Blendor) in 60 ml 0.4 N perchloric acid.