[Distribution of enzymes in the stereocilia of the ductus epididymis of rats (author's transl)]

Gamma-GT activity in the rat epididymis: effect of LHRH agonist (D-Trp 6-LHRH)

The aim of the present study was to follow the gamma-GT activity changes in the rat epididymis after withdrawal of androgens. Treatment of adult rats with the LHRH agonist D-Trp 6-LHRH led to reduce serum testosterone concentrations below the limit of detection of the assay. In the treated rats, specific activity of gamma-GT (nmol/min mg protein-1) drastically decreased in caput epididymidis. Histochemical reactions for gamma-GT completely disappeared in the initial and proximal segments but weak activity remained on the luminal plasma membranes of middle segment of the caput. In the corpus and cauda epididymidis, residual reaction for gamma-GT could be seen on the basal part of epithelial cells and on peritubular cells: Thus gamma-GT is confirmed to be androgen-dependent, but there is a regional responsiveness to withdrawal of androgen in the epididymis.

Gamma-glutamyl transpeptidase activity in the epididymis during fetal and postnatal development in rats

The histochemical and biochemical distributions of gamma-glutamyl transpeptidase (gamma-GT) were investigated in the epididymis of rats during fetal and postnatal development. In the epididymal homogenates, gamma-GT activity was detected on the fifth day after birth. A sharp increase was observed after 30 days of life in the caput homogenates. Moderate levels of the enzyme were found in the cauda epididymis. Gamma-GT is histochemically detected from the 15th day of gestation in Wolffian ducts and in 17- to 18-day-old fetuses in newly differentiated epididymal tubules. Enzyme activity, was associated with the plasma membranes (apical, lateral, and basal), was preponderant on the apical part of the epithelial cells. During the first 15 days of the postnatal life, the histochemical reaction intensities were identical from the caput to the cauda epididymidis. From the 18th day onwards, enzyme activity decreased in the corpus and in the cauda, while gamma-GT increased in the caput epididymidis, and a strong activity was found on the apical surface of epithelial cells. Weak or moderate gamma-GT activity of spermatozoa in the caput tubules, increasing steadily from caput to cauda epididymidis, suggests that gamma-GT may be related to the functional maturation of spermatozoa.

Gamma-glutamyl transpeptidase in rat epididymis: effects of castration, hemicastration and efferent duct ligation

Gamma-Glutamyl transpeptidase (gamma-GT) was studied histochemically and biochemically in the rat epididymis after castration with or without testosterone treatment, or after hemicastration and ligation of the efferent ducts. There was a strong reaction to gamma-GT in the apical part of the epithelium in the caput epididymis, while in the corpus and cauda the reaction was confined mainly to the luminal contents. Castration caused a marked decline in epithelial gamma-GT activity within 10 days. Subsequent testosterone treatment (1 mg/day for 10 days) restored gamma-GT activity in the apical surface and lumen. After hemicastration of adult rats, and after hemicastration or ligation of the efferent ducts in immature 28-day-old rats, a small but significant (P less than 0.001) decrease was observed in gamma-GT activity in the epididymal caput compared to controls. The quantities of six other enzymes (beta-N-acetylglucosaminidase, beta-galactosidase, angiotensin-converting enzyme, alanyl amino-peptidase, dipeptidyl peptidase IV, acid phosphatase) also displayed significant changes after castration and restoration of activities by testosterone treatment. However, their distribution in the caput and cauda epididymis was more even than that of gamma-GT, and the changes after castration were less drastic. It is concluded that gamma-GT is a highly sensitive androgen-dependent secretory marker in the caput epididymis and may have an important function in sperm maturation.

Dipeptidyl peptidase (DPP) IV in rat organs. Comparison of immunohistochemistry and activity histochemistry

Immunohistochemistry and activity histochemistry were used to study the localization of dipeptidyl peptidase (DPP) IV in rats. For immunohistochemistry, polyclonal as well as monoclonal anti-DPP IV antibodies were employed. The pattern of DPP IV immunoreactivity, determined with polyclonal anti-DPP IV antibody, corresponds to the histochemical pattern found for the enzymic activity of DPP IV. Immunoreactivity was present, in addition, in nerve cells, lateral membranes of certain surface epithelia, e.g., Fallopian tube, uterus and vesicular gland, in the luminal cytoplasm of e.g., vesicular gland epithelium, and in mucous cells of Brunner's gland. The monoclonal antibodies against DPP IV recognized four different epitopes (A-D) of the DPP IV molecule, and revealed that certain epitopes were not detectable by immunohistochemistry in some organs. Generally, the staining intensities for epitopes A, B, C and D decreased in that order. Usually, the monoclonal antibodies against epitopes A and B showed similar reaction patterns to those as obtained with the polyclonal antibody. Epitope D was recognized in the lumen of the duct system of exocrine glands and the intestine. Furthermore, high reactivity of this epitope was detected in goblet cells of the intestine, where no DPP IV activity was present.

[Peptidases II. Localization of dipeptidylpeptidase IV (DPP IV). Histochemical and biochemical study]

Fresh frozen, unfixed, chloroforme-acetone treated or freeze-dried cryostat sections or sections from aldehyde-fixed blocks of tissue were tried for the histochemical investigation of dipeptidylpeptidase IV (DPP IV) with L-glycyl-L-prolyl(gly-pro)-naphthylamides as substrates and stable or unstable diazonium salts for simultaneous coupling and various buffers, pH 5--7.5 in rats, mice, guinea-pigs, cats, rabbits, hamsters and human enterobiopsies. The best results are obtained with 1.7--3.4 mM gly-pro-4-methoxy-2-naphthylamide and 1 mg Fast Blue B/ml or (with some limitations) 0.025 ml hexazotized new fuchsine/ml in 0.1 M cacodylate or phosphate buffer, pH 7.5 and unfixed sections for the demonstration of the total activity of DPP IV and freeze-dried celloidin-mounted cryostat sections for the precise localization of the enzyme or the detection of lysosomes, Golgi apparatus and secretion granules sections from aldehyde fixed tissue blocks are only suitable to study the lysosomal hydrolysis of gly-pro-naphthylamides between pH 5 and 7 when hexazotized p-rosaniline or new fuchsine are employed. DPP IV is firmly bound to strutures and shows species- and organ-dependent differences. In general, the enzyme occurs in the capillary endothelium, sinusoidal cells, perineurium, epithelial cells of intercalated and striated ducts, microvillous zone of intestinal crypts and villi, uterus, Fallopian tubes, ductus epididymis and proximal renal tubules, hepatocyte and lymphocyte membrane, plasmalemma of pseudostratified and transient epithelia and in the capsules and interstitium of many organs. These sites of activity can be completely inhibited by diisopropyl fluorophosphate and partially by Pb2+; Mg2+, Mn2+, Co2+ EDTA are without any influence. Phenantrolin may activate DPP IV. The biochemical assay works with 10 mM gly-pro-2-naphthylamide in 0.1 M cacodylate buffer, pH 7; the enzyme activity is determined fluorometrically in guinea-pig and rat organs; the data confirm and enlarge the species- and organ-dependent differences revealed by histochemistry. Compared with other dipeptide as well as tripeptide and amino acid naphthylamides the results obtained for DPP IV suggest a peptidylpeptidase which seems to be involved in other metabolic processes beside the degradation of collagen.