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J. SUOMINEN and B. P. SETCHELL

Summary.

Compared with blood plasma, rete testis fluid (RTF) from rams was found to contain a higher concentration per unit volume of the enzymes that occur in the sperm acrosome and in the kinoplasmic droplet, but the levels of these enzymes could be reduced by high-speed centrifugation. Other enzymes present in blood plasma were also found in RTF but at a lower concentration per unit volume. Because of the low concentration of protein in RTF, however, the activity of most of these enzymes per unit weight of protein was higher in RTF than in blood plasma. The concentrations of these enzymes and the total protein concentrations were only slightly reduced by high speed centrifugation. There was no appreciable concentration of the X-isoenzyme of lactic dehydrogenase in RTF and the activity of most enzymes per unit weight of protein was less in RTF than in the testis.

Epididymal plasma and RTF from rams and boars were found to contain appreciable concentrations of an inhibitor of trypsin and the activity of the inhibitor per unit weight of protein was comparable with the activity in seminal plasma.

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J. SUOMINEN, S. MULTAMÄKI and MIKKO NIEMI

Summary.

High dipeptidase and aminopeptidase activity is present in human seminal plasma. The two activities can be easily and clearly separated from each other by chromatographic procedures. Each of the three dipeptidase fractions has characteristic substrate specificity but is not affected by divalent metals. The seminal aminopeptidase activity is inhibited by EDTA and activated by cobalt.

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J. SUOMINEN, R. ELIASSON and M. NIEMI

Summary.

Proteolytic activity, acid phosphatase activity and fructose concentration were measured in seminal plasma from 205 human semen samples. Certain routine sperm characteristics were also determined. High fibrinolytic activity was found and TAME-esterase and proteinase activity was also present in all specimens. The activity of all the proteolytic enzymes correlated positively with the acid phosphatase activity suggesting the prostate gland to be the origin of the enzymes. TAME-esterase activity was inversely related to the seminal fructose content. No correlation was observed between sperm characteristics and the seminal proteolytic enzymes. The specimens with abnormal viscosity usually contained low proteinase activity.

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J. SUOMINEN, M. H. KAUFMAN and B. P. SETCHELL

One of the enzymes probably involved in sperm penetration through the outer layers of the ovum is a trypsin-like enzyme, called acrosin because of its location in the acrosome. This enzyme is inhibited by substances found in semen and in the secretion of seminal vesicles of several mammalian species (see Werle & Zickgraf-Rüdel, 1972). It is generally thought that the spermatozoa mix with these inhibitors during ejaculation, and a complex between the inhibitors and the acrosin is formed at that time (Zaneveld, Polakoski, Robertson & Williams, 1971; Werle & Zickgraf-Rüdel, 1972). Removal of these inhibitors from the acrosome is supposed to be an essential part of the process of capacitation and the acrosome reaction (see Bedford, 1970). Several attempts have been made to prevent fertilization with synthetic or natural trypsin inhibitors, and