Abstract. The usefulness of plasminogen activators (PAs) in the follow-up of the secretory function of the prostate in culture, as well as the hormonal control of these secretory proteins was studied. Organ culture of rat ventral prostate was used as an experimental model. PA secreted into the culture medium during the two weeks' culture period was of the urokinase-type in all culture conditions, as determined by zymography. The highest activities at the end of culture were found in the involuting prostate in cultures without any hormones. As the epithelial component is strongly reduced in the involuted explants, these high activities were suggested to be derived from stroma. Corticosterone (10−7 mol/l) and insulin (80 U/l) reduced significantly the secretion of PA, and this reduction was attenuated when the favourable effect of these hormones on the maintenance of morphology and tissue weight was taken into account. Testosterone (10−7 mol/l) increased significantly the secretion of PA in all hormone-treated cultures, which could be due to the increased secretory activity of the epithelium. Interactions between the hormones were significant, i.e. the effects of the hormone combinations were different and could not be calculated from the separate effects of these hormones. Even though the general growth and function of the prostate is strictly androgen-controlled, these results suggest that the control of PA secretion is multihormonal.
Paula Martikainen, Jyrki Suominen and Kimmo Vihko
Kimmo K. Vihko, Jorma Toppari, Olli Saksela, Jyrki J. O. Suominen and Martti Parvinen
Abstract. In the seminiferous epithelium, Sertoli cells secrete plasminogen activator (PA) under regulation of follicle stimulating hormone, cyclic AMP and neighbouring spermatogenic cells. Recent observations suggest that preleptotene spermatocytes upon their release from the basement membrane of the seminiferous tubule are important regulators of PA secretion. To study further the role of PA's in the seminiferous tubules, we have analyzed the endogenous levels and secretion rates of PA at various ages during postnatal development, and performed biochemical analyses of the types of PA in the testis and spent media from seminiferous tubular cultures. Cyclic secretion of PA started at the age of 28 days, and from 40 days onwards, the high secretion rates were localized in stages VII and VIII of the cycle of the seminiferous epithelium. The secreted PA is most obviously of the urokinase type; both urokinase-type and tissue-type PA-like activities were found in seminiferous tubular homogenates. The increase in testicular PA levels concomitant to the onset of meiosis in the epithelium was due to the urokinasetype PA-like activity.
Kimmo K Vihko, Erkki Kujansuu, Pertti Mörsky, Ilpo Huhtaniemi and Reijo Punnonen
Vihko KK, Kujansuu E, Mörsky P, Huhtaniemi I, Punnonen R. Gonadotropins and gonadotropin receptors during the perimenopause. Eur J Endocrinol 1996;134:357–61. ISSN 0804–4643
Twenty-two perimenopausal patients (aged 47–56 years) admitted for elective abdominal hysterectomy and salpingo-oophorectomy were selected to understand better the clinical significance of increasing gonadotropin levels as an indicator of target organ responsiveness. Prior to anesthesia, blood was drawn from the patients for subsequent analyses of serum follicle-stimulating hormone (FSH), luteinizing hormone (LH) and 17β-estradiol (E2) levels. Ovarian tissue was obtained during surgery and frozen at −70°C for subsequent analyses for FSH and LH receptor content. The phase of the menstrual cycle of the patients or postmenopause was determined by serum gonadotropin and E2 levels and histological evaluation of the endometrium. Patients with no detectable FSH receptors showed significantly higher serum FSH and LH levels (4.7- and 4.3-fold, respectively) when compared to patients with detectable FSH receptors; FSH receptors were present in 27% of the patients, LH receptors were present in 68% of the patients and a negative correlation was found between serum LH levels and ovarian LH receptors. In postmenopausal patients, neither FSH receptors nor LH receptors were detectable. High serum gonadotropin levels in perimenopausal patients thus suggest the existence of low or undetectable ovarian gonadotropin receptor levels.
Kimmo Vihko, Department of Obstetrics and Gynecology, Tampere University Hospital, PO Box 2000, FIN-33521 Tampere, Finland
Kimmo Kontula, Olli Jänne, Reijo Vihko, Evert de Jager, Jacob de Visser and Filippus Zeelen
Progesterone-binding proteins from human, rabbit, sheep and guinea pig myometrial cytosol, all induced with oestradiol, as well as from pregnant guinea pig myometrium and plasma were investigated. The physico-chemical properties of the oestradiol-induced binding proteins were very similar in all the species studied.
In all, 63 steroids were tested for their ability to compete with tritiated progesterone for the binding sites on these six proteins and their relative affinities were determined. The studies reveal that the ligand specificities of oestrogen-induced myometrial binding proteins from human, rabbit and sheep are rather similar, whereas that from guinea pig myometrium has different binding characteristics. The properties of the binding proteins from pregnant guinea pig uterus and plasma differ substantially from all of the induced proteins. It is clear from the different physico-chemical characteristics and binding specificities that the oestrogen-induced myometrial protein of the guinea pig is not the same as that which appears in the myometrium and plasma during pregnancy.
The binding energies of the well bound progestational compounds were of the order of −12 Kcal/mole, half of which stems from the interaction of the steroid nucleus with the protein. The specific interaction of the protein with the two functional groups, the 3-keto-4-ene system and the acetyl side chain each contributed −3 Kcal/mole. In the case of the rabbit, sheep and human proteins a 17α-ethynyl-17β-hydroxyl function could replace the acetyl side chain.
For a large number of steroids reasonable agreement existed between the degree of binding to the rabbit myometrial protein and in vivo biological activity (Clauberg-McPhail test) in the same species. The data suggest that as far as the binding aspect is concerned, the rabbit is an appropriate model for assessing the biological activity of compounds under development for human application. The in vitro binding system is also a useful tool to assess whether steroids need to be bio-activated before eliciting a biological response.