Measurements of total rat testicular protein carboxyl-methylase (PCM) activity at various ages ranging from 10 to 90 days showed a rapid (fivefold) increase between 20 and 30 days, coincident with the occurrence of haploid germ cells. When partially purified testicular enzyme, at different ages, was fractionated by isoelectric focusing, the activity of the individual PCM isomers displayed clear differences in the time at which maximal activity was reached. The most acid PCM isoenzyme (pI 6.1) was the dominant isoform in the immature testis and exhibited the highest increase in activity between 20 and 30 days of age. During the same age interval, the activity of the other two isoenzymes (pI 6.7 and 7.4) increased only slightly. At 50 days, while the isofocusing profile revealed no additional increase in the activity of the acid isoform (pI 6.1) and only a doubling in the activity of the second isomer (pI 6.7), the most basic isoenzyme displayed a drastic increment in specific activity (approximately sixfold when compared to 30 days). This indicates that the PCM isozymes have different cellular localization in the seminiferous tubules. The acid isomer (pI 6.1) appears to be associated to the early stages of spermatogenesis and may represent both germ cell and somatic cell PCM. The basic isomer (pI 7.4) may be specific for germ cells (spermatids), and is most likely associated with the later stages of germ cell maturation.

Annals of the New York Academy of SciencesVolume 383, Issue 1 p. 440-441 CHARACTERIZATION OF PROTEIN CARBOXYL-METHYLASE IN THE RAT TESTIS L. Cusan, L. Cusan Institute of Pathology Rikshospitalet Oslo, NorwaySearch for more papers by this authorJ. O. Gordeladze, J. O. Gordeladze Institute of Pathology Rikshospitalet Oslo, NorwaySearch for more papers by this authorM. Parvinen, M. Parvinen Institute of Biomedicine Department of Anatomy University of Turku Turku, FinlandSearch for more papers by this authorV. Hansson, V. Hansson Institute of Pathology Rikshospitalet Oslo, NorwaySearch for more papers by this author L. Cusan, L. Cusan Institute of Pathology Rikshospitalet Oslo, NorwaySearch for more papers by this authorJ. O. Gordeladze, J. O. Gordeladze Institute of Pathology Rikshospitalet Oslo, NorwaySearch for more papers by this authorM. Parvinen, M. Parvinen Institute of Biomedicine Department of Anatomy University of Turku Turku, FinlandSearch for more papers by this authorV. Hansson, V. Hansson Institute of Pathology Rikshospitalet Oslo, NorwaySearch for more papers by this author First published: June 1982 https://doi.org/10.1111/j.1749-6632.1982.tb23189.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume383, Issue1The Cell Biology of the TestisJune 1982Pages 440-441 RelatedInformation

Adenylyl cyclase (AC) and protein carboxyl methylase (PCM) activities in human ejaculated spermatozoa were measured in 31 men being evaluated for infertility at the Infertility Clinic. The spermatozoal Mn2+-sensitive AC activities ranging between zero and 1.4 nmol cyclic adenosine monophosphate (cAMP)/10(9) cells/min, was positively correlated with motility index [% motile sperm X degree (0-4)] (r = 0.72, rho less than 0.05). This confirms a role for cAMP in human sperm motility. PCM activities, ranging between zero and 160 pmoles (CH3OH/10(9) cells/min), were significantly correlated with AC activities (r = 0.86, p less than 0.001). However, PCM activities were not positively correlated with motility index (p = 0.065). PCM most probably is a factor involved in spermatozoal motility since two patients suffering necrospermia possessed spermatozoa deficient in both AC and PCM activities.

An examination of the activity of the Mn2+-dependent adenylyl cyclase (AC) in fine needle biopsies from human testes was made. Simultaneously the DNA distribution patterns in suspensions of testicular cells derived from the same patients have been determined. The DNA distribution patterns were estimated by microflow fluorimetry (MFF) after straining with fluorochrome (ethidium bromide). Thus, AC activity could be assessed and correlated with the relative number of haploid (1C = spermatids), diploid (2C = spermatogonia and testicular somatic cells), and tetraploid (4C = primary spermatocytes) cells. Testicular Mn2+-dependent AC activities varied between 0 and 8.4 pmol cyclic adenosine monophosphate (cAMP)/mg protein/min and were highly correlated with the contents of haploid (1C) germ cells (spermatids) (r = 0.62, p less than 0.01). There was no correlation between Mn2+-dependent AC activity and diploid or tetraploid cells. This indicates that the Mn2+-dependent AC activity in the human testis, like in the rat and mouse, may be exclusively localized to haploid germ cells. An inverse correlation between plasma FSH and Mn2+-dependent AC activities indicated reduced inhibin secretion in situations where the Sertoli cells did not maintain the testicular germ cell production.

In the present study we have examined the effects of gonadotrophin releasing hormone (LHRH), sex steroids and glucocorticoids on the binding of LHRH to receptors in the pituitary of male intact and castrated rats. In intact rats, LHRH (10 microgram/day) treatment for 11 days caused a significant increase in LHRH binding, whereas testosterone (500 microgram/day) or oestradiol (50 microgram/day) were inhibitory. 17-hydroxyprogesterone and dexamethasone were without effects. In castrated rats, LHRH caused a marginal decrease in LHRH binding. Much greater inhibition was observed with testosterone and oestradiol. 17-hydroxyprogesterone reduced binding to that of intact controls, whereas dexamethasone was ineffective. When different doses of sex steroids were tested, both oestradiol, testosterone and 5 alpha-dihydrotestosterone inhibited LHRH in a dose-dependent manner. The lowest doses of steroids causing significant inhibition of LHRH binding in castrated animals were 0.5, 50 and 500 microgram/day for oestradiol, 5 alpha-dihydrotestosterone and testosterone, respectively. The present study shows that pituitary receptors for LHRH are regulated both by sex steroids and LHRH itself.

Specific blocks in the steroidogenic pathway involved in the production of testosterone by the Leydig cell can be irreversible due to the genetically determined absence of a specific enzyme, or reversible because of specific inhibitory effects of steroids. In the former case, the irreversible lesions are responsible for pathologically lower testosterone levels resulting in various forms of pseudohermaphroditism. In the latter case (caused by steroids), such inhibition is probably mediated via specific receptors in Leydig cells and may involve processes of transcription and translation. In the case of the reversible lesion, this may constitute a physiological mechanism by which the secretion of testosterone by the testis can be locally controlled, especially after periods of intense LH stimulation. The mediator of some of the most documented reversible lesions appear to be an oestrogen. In addition to such lesions, mechanisms causing the activation of specific metabolising enzymes also appear to play a role in the alteration of the secretory response under certain conditions. Finally the differential activation or inhibition of certain of the steroidogenic enzymes during development in various species may serve to alter testicular steroid secretion qualitatively, without affecting the steroidogenic potential of the cell. Such subtle alterations in the pattern of steroid secretion in certain species may, by altering the availability of biologically active androgens, serve to control the degree of peripheral androgenisation and the induction of puberty.

The activities of two testicular enzymes, protein carboxylmethylase (PCM) and Mn2+-dependent adenylyl cyclase (AC), both of which have been shown to be primarily localized in haploid germ cells, were assessed at various stages of the spermatogenic cycle in the rat. The two enzymes displayed the lowest specific activity at stages VII and VIII of the cycle. A gradual increase in the activity of both enzymes was observed from stages XII to IV–V with maximal levels at stages II–III. During the study a highly positive correlation (r = 0.91, P<0.001) was seen between PCM and AC activities. These results show a close parallelism and a stage-dependent variation of PCM and AC activities during the seminiferous epithelial cycle in the rat.

The physicochemical and molecular properties of testicular Protein Carboxyl Methylase (PCM) have been studied. The testicular enzyme was stable at high ionic strength, independent of metal ions and resistant to reducing or alkylating agents, and displayed a narrow pH optimum of pH 5.8-6.0. The enzyme had a molecular weight of approximately 25,000 daltons and a Km for S-adenosyl-L-methionine (SAM) of 1.3 microM. Varying concentrations of gelatine (exogenous methyl acceptor protein) did not change the affinity of the enzyme for SAM. The molecular properties of the enzyme were characterized using gel filtration, hydroxyapatite and DEAE-cellulose chromatography, and isoelectric focusing. Three charge isomers exhibiting PCM activity were isolated with pI values of 6.1, 6.7, and 7.35 while comparative data from the pituitary gland revealed primarily the presence of the most acid isozyme (pI 6.1). These results suggest that the different testicular charge isozymes may be involved in the selective methylation of specific testicular proteins.