Sexual Fate Reprogramming in the Steroid-Induced Bi-Directional Sex Change in the Protogynous Orange-Spotted Grouper,Epinephelus coioides

Androgen administration has been widely used for masculinization in fish. The mechanism of the sex change in sexual fate regulation is not clear. Oral administration or pellet implantation was applied. We orally applied an aromatase inhibitor (AI, to decrease estrogen levels) and 17α-methyltestosterone (MT, to increase androgen levels) to induce masculinization to clarify the mechanism of the sex change in the protogynous orange-spotted grouper. After 3 mo of AI/MT administration, male characteristics were observed in the female-to-male sex change fish. These male characteristics included increased plasma 11-ketotestosterone (11-KT), decreased estradiol (E2) levels, increased male-related gene (dmrt1, sox9, and cyp11b2) expression, and decreased female-related gene (figla, foxl2, and cyp19a1a) expression. However, the reduced male characteristics and male-to-female sex change occurred after AI/MT-termination in the AI- and MT-induced maleness. Furthermore, the MT-induced oocyte-depleted follicle cells (from MT-implantation) had increased proliferating activity, and the sexual fate in a portion of female gonadal soma cells was altered to male function during the female-to-male sex change. In contrast, the gonadal soma cells were not proliferative during the early process of the male-to-female sex change. Additionally, the male gonadal soma cells did not alter to female function during the male-to-female sex change in the AI/MT-terminated fish. After MT termination in the male-to-female sex-changed fish, the differentiated male germ cells showed increased proliferating activities together with dormancy and did not show characteristics of both sexes in the early germ cells. In conclusion, these findings indicate for the first time in a single species that the mechanism involved in the replacement of soma cells is different between the female-to-male and male-to-female sex change processes in grouper. These results also demonstrate that sexual fate determination (secondary sex determination) is regulated by endogenous sex steroid levels.     

Influence of sex hormones on ethanol-induced gastric haemorrhagic erosions in rats.

The role of sex hormones in the pathogenesis of ethanol-induced gastric erosions was investigated following the recent observation that ethanol generates more severe gastric damage in male rats. Female and male Wistar rats aged 110 +/- 6 days were used. Intact female, ovariectomized female, intact male, orchidectomized male and cyproterone acetate-pretreated (this compound a testosterone antagonist) male rats were investigated. 1 ml of 75% ethanol was used to induce gastric lesions. The extent of the erosions was determined planimetrically 60 min after ethanol administration. The plasma testosterone and 17-beta-oestradiol levels were checked by radioimmunoassay (RIA) in gonadectomized rats. Ethanol generates more severe lesions in male rats. Orchidectomy and cyproterone acetate treatment each reduced the extent of ethanol-induced gastric erosions in male rats. Ovariectomy had no effect in this model. The plasma testosterone and 17-beta-oestradiol levels were significantly reduced after gonadectomy. It is concluded that endogenous testosterone plays an aggressive role in the pathogenesis of ethanol-induced gastric erosions in rats.     

Gender differences in the vasomotor effects of different steroid hormones in rat pulmonary and coronary arteries.

It is well recognised that oestrogens possess vasodilatory properties, and similar responses to testosterone have been demonstrated. However, vasomotor effects of other steroid hormones have not been well described. Direct comparisons of the relative vasoactivity of different steroid hormones in different vascular beds in male and female genders have not been made. Coronary and pulmonary arteries from adult Wistar rats were mounted in a wire myograph, loaded to 100 and 17 mmHg respectively, maximally pre-contracted with 1 x 10(-4) M prostaglandin-F-2-alpha, and dose response curves to 1 x 10(-6) to 1 x 10(-3) or 3 x 10(-3) M of 17 beta-oestradiol, testosterone, progesterone, and cortisol dissolved in water were constructed. Addition of each steroid hormone caused acute, dose dependent dilatation in coronary and pulmonary vessels. In coronary arteries the order of activity was testosterone > progesterone > 17 beta-oestradiol > cortisol, p < 0.001. In pulmonary arteries, the order of activity was progesterone > testosterone > cortisol > 17 beta-oestradiol, p < 0.001. Pulmonary arteries from male animals were more sensitive to the effects of testosterone than those from female animals, p = 0.003, whereas coronary arteries from female animals were more sensitive to the effects of 17 beta-oestradiol than those from male animals, p < 0.001. We have demonstrated significant differences in the in vitro vasomotor effects of different steroid hormones in two distinct vascular beds. Gender differences in vasomotor responses to steroid hormones may play a role in the aetiology of vasospastic diseases.     

Effects on the male endocrine system of long-term treatment with gonadotropin-releasing hormone agonists and estrogens in male-to-female transsexuals.

We studied hormonal changes resulting from long-term treatment with gonadotropin-releasing hormone agonist and 17beta estradiol valerate in 40 healthy middle-aged male-to-female transsexuals over a period of two years. All of the participants received injections of 3.8 mg goserelin acetate every four weeks in combination with 6 mg oral 17beta estradiol valerate per day for cross-sex hormone treatment for male-to-female transsexuals. There was a significant reduction in the levels of serum luteinizing hormone and follicle-stimulating hormone to the hypogonadal stage. Mean testosterone levels decreased by 97% to 0.52 and 0.59 nmol/l after 12 months and 24 months, respectively. There was a significant reduction in dehydroepiandrosterone sulfate by 37% after 12 months and 43% after 24 months, and androstendione by 29% after 12 months and 27% after 24 months, respectively. Cortisol levels were reduced by 43% and 50%, respectively. Estrogen levels were significantly increased from 77.51 to 677 after 12 months and 661 pmol/l after 24 months. Sex hormone-binding globulin and corticoid-binding globulin levels were significantly increased after 12 and 24 months. There was a significant decrease in all measured androgen fractions and cortisol during long-term treatment with gonadotropin-releasing hormone agonist and 17beta estradiol valerate. Apart from suppression of testicular hormone production, one possible interpretation is that treatment with long-term gonadotropin-releasing hormone agonist and 17beta estradiol valerate influences adrenal hormone levels in healthy middle-aged male-to-female transsexuals. Cortisol serum levels may be decreased due to estrogen-induced increase in corticoid-binding globulin.     

Effects of co-administration of estrogen and androgen on induction of sex reversal in the medaka Oryzias latipes

To investigate how estrogen and androgen affect each other in inducing sex reversal in the medaka, O. Iatipes, 17β-estradiol (E2) and 17α-methyldihydrotestosterone (MDHT) were co-administered by a convenient method for hormonal treatment, in which freshly fertilized eggs were immersed for 24 h in saline containing either or both of the two sex steroids in different concentrations and/or ratios. The minimal concentrations of E2 and MDHT sufficient to induce the maximal rate of sex reversal from male to female and from female to male were 500 ng/ml and 2.5 ng/ml, respectively, both of which were referred to as the most efficacious dose (MED), and each equivalent for the inducing potency in sex reversal. E2 and MDHT, when simultaneously administered at MED, greatly suppressed each other to induce each corresponding sex reversal. Thus, the present experimental results indicate that E2 and DMHT are antagonists that induce corresponding sex reversal, and suggest that genotypic sex in the medaka might be modified through an unknown factor of common affinity to both sex steroids, by which the pathway of differentiation of either sex could be switched at the early stages of development far before gonadal sex differentiation.     

Sparing a testis during vaginoplasty in male-to-female transsexuals: does it benefit our patients?

Testosterone and its metabolite dihydrotestosterone are the libido hormones for the male, vital to sex drive and sexual function. Fear of loss of libido and orgasm is the main reason to retain at least one testis in male-to-female transsexuals during vaginoplasty. We report on four South American transsexual patients in whom we resected a remaining testis to illustrate the superfluity of retaining it. Because there are multiple reasons for castration, we advise that bilateral orchidectomy be performed in the course of sex reassignment surgery for male-to-female transsexuals.     

Experimental evidence that corticosterone affects offspring sex ratios in quail

Recent studies have shown that some species of birds have a remarkable degree of control over the sex ratio of offspring they produce. However, the mechanism by which they achieve this feat is unknown. Hormones circulating in the breeding female are particularly sensitive to environmental perturbations, and so could provide a mechanism for her to bias the sex ratio of her offspring in favour of the sex that would derive greatest benefit from the prevailing environmental conditions. Here, we present details of an experiment in which we manipulated levels of testosterone, 17beta-oestradiol and corticosterone in breeding female Japanese quail (Coturnix coturnix japonica) using Silastic implants and looked for effects on the sex ratio of offspring produced. Offspring sex ratio in this species was significantly correlated with faecal concentrations of the principal avian stress hormone, corticosterone, and artificially elevated levels of corticosterone resulted in significantly female-biased sex ratios at laying. Varying testosterone and 17beta-oestradiol had no effect on sex ratio alone, and faecal levels of these hormones did not vary in response to corticosterone. Our results suggest that corticosterone may be part of the sex-biasing process in birds.     

Wind tunnel studies on the effects of secondary sex pheromone components on the behaviour of male Egyptian cotton leafworm moths, Spodoptera littoralis

ABSTRACT. The responses of adult male Spodoptera littoralis (Boisd.) (Noctuidae) to components of the female sex pheromone were examined in a wind tunnel. The responses of male moths from both Egyptian and Cretan stocks to the primary 'attractant' (Z, E)-9,11 tetradecadienyl acetate (III), were compared with the responses to III combined with various percentages of the secondary components tetradecyl acetate (I), (Z)-9-tetradecenyl acetate (IIA), (E)-11-tetradecenyl acetate (IIB), IIA and IIB combined, and(Z, E)-9,12-tetradecadienyl acetate (IV). Analysis of the flight behaviour recorded on videotape showed that with one exception (IV), the secondary components increased the males' success in reaching the source and increased the length of time they spent at the source. In most cases, increasing the relative percentage of the secondary component caused a reduction in the number of males responding. The results are compared with those obtained in field trials with S.littoralis.     

Effect of testosterone concentration on the intensity of 5alpha-dihydrotestosterone and 17beta-oestradiol formation

The culture of human male foreskin fibroblasts was incubated with various concentrations of testosterone in the medium. It has been shown that the minimum formation of 17beta-oestradiol and 5alpha-dihydrotestosterone occurs at physiological testosterone concentrations. Any deviation of testosterone concentration, both up and down, was accompanied by an increase in the formation of 17beta-oestradiol and 5alpha-dihydrotestosterone.     

Simultaneous increase in the aromatization of testosterone into estrogens and secretion of inhibin by Sertoli cells in culture

17 beta oestradiol and inhibin production by Sertoli cells has been investigated in vitro. In basal conditions, 17 beta-oestradiol secretion is weak whereas inhibin production is undetectable on days 7 and 9 of culture. Addition of PMSG (FSH-like gonadotrophin) and testosterone to the culture medium induces a simultaneous increase in 17 beta-oestradiol and inhibin production. PMSG alone has no effect neither on inhibin nor on 17 beta-oestradiol secretion. Testosterone alone significantly increases 17 beta-oestradiol and inhibin production. Human chorionic gonadotrophin (LH-like gonadotrophin) does not modify inhibin secretion. Dihydrotestosterone stimulates inhibin production without affecting oestrogens secretion. Thus, stimulation of aromatization of testosterone into 17 beta-oestradiol is associated with an increase of inhibin production, but this effect seems to be due to a direct action of androgens.     

Regulatory effects of testosterone and 17 beta-oestradiol on the metabolism of dimethylnitrosamine by renal and hepatic microsomal enzymes from BALB/c mice

Previous investigations with BALB/c mice have demonstrated that no sex-related differences exist in the ability of liver microsomal fractions (S-9) to biotransform dimethylnitrosamine (DMN) to its active mutagenic metabolites as evidenced by bacterial screening assays. In contrast, kidney microsomal enzymes from adult male BALB/c mice and not from females, castrates, and immature animals, were capable of activating DMN. The present study was designed to test the effects of testosterone and oestradiol on DMN bioactivation by hepatic or renal microsomal enzymes. Mutagenic assays were performed using liver and kidney microsomal enzymes with the histidine deficient mutant Salmonella typhimurium TA100. Results indicate that testosterone treatment of female BALB/c mice resulted in an increase in the ability of their renal microsomal enzymes to metabolize DMN to its active mutagenic intermediates. Renal microsomal enzymes from female mice treated with 17 beta-oestradiol had no effect on DMN metabolism. However, the ability of the renal microsomal enzymes treated with 17 beta-oestradiol to bioactivate DMN was significantly decreased in males.     

Oestrogen regulates male aggression in the non-breeding season

Extensive research has focused on territorial aggression during the breeding season and the roles of circulating testosterone (T) and its conversion to 17beta-oestradiol (E2) in the brain. However, many species also defend territories in the non-breeding season, when circulating T-levels are low. The endocrine control of non-breeding territoriality is poorly understood. The male song sparrow of Washington State is highly territorial year-round, but plasma T is basal in the non-breeding season (autumn and winter). Castration has no effect on aggression in autumn, suggesting that autumnal territoriality is independent of gonadal hormones. However, non-gonadal sex steroids may regulate winter territoriality (e.g. oestrogen synthesis by brain aromatase). In this field experiment, we treated wild non-breeding male song sparrows with a specific aromatase inhibitor (fadrozole, FAD) using micro-osmotic pumps. FAD greatly reduced several aggressive behaviours. The effects of FAD were reversed by E2 replacement. Treatment did not affect body condition or plasma corticosterone, suggesting that all subjects were healthy These data indicate that E2 regulates male aggression in the non-breeding season and challenge the common belief that aggression in the non-breeding season is independent of sex steroids. More generally, these results raise fundamental questions about how sexual and/or aggressive behaviours are maintained in a variety of model vertebrate species despite low circulating levels of sex steroids or despite castration. Such non-classical endocrine mechanisms may be common among vertebrates and play an important role in the regulation of behaviour.     

DNA fragmentation, DNA repair and apoptosis induced in primary rat hepatocytes by dienogest, dydrogesterone and 1,4,6-androstatriene-17beta-ol-3-one acetate

Four steroids that share the 17-hydroxy-3-oxopregna-4,6-diene structure - cyproterone acetate, chlormadinone acetate, megestrol acetate, and potassium canrenoate - have been shown previously to behave with different potency as liver-specific genotoxic agents, the response being markedly higher in female than in male rats, but similar in humans of both genders. In this study, performed to better define the relationship between chemical structure and genotoxicity, dydrogesterone (DGT) with double bonds C4=C5 and C6=C7, dienogest (DNG) with double bonds C4=C5 and C9=C10, and 1,4,6-androstatriene-17beta-ol-3-one acetate (ADT) with double bonds C1=C2, C4=C5 and C6=C7, were compared with cyproterone acetate (CPA) for their ability to induce DNA fragmentation and DNA repair synthesis in primary cultures of hepatocytes from three rats of each sex. At subtoxic concentrations, ranging from 10 to 90 microM, all four steroids consistently induced a dose-dependent increase of DNA fragmentation, which in all cases was higher in females than in males; their DNA damaging potency decreased in the order CPA > DNG > ADT > DGT. Under the same experimental conditions, the responses provided by the DNA repair-synthesis assay were positive or inconclusive in hepatocytes from female rats and consistently negative in hepatocytes from male rats. In the induction of apoptotic cells, examined in primary hepatocytes from female rats, CPA was more active than ADT and DGT, and DNG was inactive. Considered as a whole these findings suggest that a liver-specific genotoxic effect more marked in female than in male rats might be a common property of steroids with two or three double bonds.     

The role of thyroid and adrenal cortical hormones in the modulation of the gonadal function in birds

The role of the thyroid gland in modulating the gonad function depends on the functional state of the gonads. In sexually inactive (short-day's) male Japanese quails, thyroidectomy and thyroxine treatment prove ineffective. Thyroxine administered simultaneously with photo-gonadostimulation inhibits the maturation of the gonads: the testes decrease in weight, the metabolic clearance rate of testosterone accelerates, resulting in a decrease in the plasma level, and androsterone production increases. Photo-gonadostimulation of thyroidectomized quails shows down the growth of the testicles and decreases the plasma testosterone level. The latter change can be related to the inhibition of the secretion rate. Both thyroidectomy and thyroxine administration performed in mature male quail, cock, pigeon or Peking duck lower the testosterone plasma level. The loss of the testicular weight is more expressed in hyperthyroid than in normal quails, referring to the role of the increased thyroxine level in the seasonal (summer) gonadal involution. Thyroidectomy performed on sexually inactive (short-day's) female Japanese quails does not affect the ovarian structure, but 17 beta-oestradiol and testosterone plasma levels show a slight increase. Thyroxine administration is followed by a moderate increase in the size of the white follicles, and an increase of both the progesterone and the oestrogen concentrations. Photo-gonadostimulation of thyroidectomized quails causes an inhibition of the mechanism of ovulation without inhibiting the development of the yellow follicles. A similar phenomenon has been observed in mature quails and domestic fowls after thyroidectomy. In both cases, an unbalanced secretion of the sexual steroids occurs: the 17 beta-oestradiol plasma level declines, while the progesterone level increases. Simultaneous application of thyroxine and photo-gonadostimulation on female quails inhibits gonadal maturation: the growing of the yellow follicles slows down. In thyroxine-treated birds, the plasma level of all of the sexual steroids shows a considerable decrease, which can be attributed to a reduced secretion rate and increased metabolic clearance. In hatching turkeys, we failed to observe the increase of the T3 level described for other species, however, the T4 plasma concentration was increasing at the early period of hatching. The role of the thyroid hormones in the development of hatching has not been cleared up so far. Corticosterone administration shows a slight stimulating effect on the gonadal function of sexually inactive male and female Japanese quails.(ABSTRACT TRUNCATED AT 400 WORDS)     

Estrogen treatment effects on cognition, memory and mood in male-to-female transsexuals

Gonadal hormones, particularly estrogens, have been suggested to influence memory and cognitive tasks that show sex differences. Previously, we reported that male-to-female (M-F) transsexuals undergoing estrogen treatment for sex re-assignment scored higher on verbal Paired Associate Learning (PAL) than a transsexual control group awaiting estrogen treatment. The present study used a more robust design to examine further associations between estrogen and cognition. We assessed additional aspects of memory, including visual, spatial, object and location memory, other cognitive abilities that show reliable sex differences, including verbal and visual-spatial abilities, and mood variables that could mediate associations between estrogen and cognition. In addition to comparing groups of individuals on and off estrogen, we used two repeated measures designs (AB and BA). The AB group was tested prior to hormone treatment and then again after treatment had begun; the BA group was tested while on estrogen treatment and then again when hormones had been withdrawn prior to surgery. Few changes in memory or cognition were observed, and changes that were observed were not consistent across study designs. The lack of significant effects did not relate to mood changes or to the sexual orientation of participants. These findings suggest that estrogen treatment associated with sex change for M-F transsexuals has little or no influence on sex-typed aspects of cognition or memory.     

Psychopathological Profiles in Transsexuals and the Challenge of Their Special Status among the Sexes

Objective

Investigating psychopathological profiles of transsexuals raises a very basic methodological question: are control groups, which represent the biological or the phenotypic sex, most suited for an optimal evaluation of psychopathology of transsexuals?

Method

Male-to-female (MtF) (n=52) and female-to-male transsexuals (FtM) (n=32), receiving cross-sex hormone treatment, were compared with age matched healthy subjects of the same genetic sex (n=178) and with the same phenotypic sex (n=178) by means of the Symptom Check List-90-Revisited instrument (SCL-90-R). We performed analyses of covariance (ANCOVA) to test for group and sex effects. Furthermore, we used a profile analysis to determine if psychopathological symptom profiles of transsexuals more closely resemble genotypic sex or phenotypic sex controls.

Results

Transsexual patients reported more symptoms of psychopathological distress than did healthy control subjects in all subscales of the SCL-90-R (all p<0.001), regardless of whether they were compared with phenotype or genotype matched controls. Depressive symptoms were more pronounced in MtF than in FtM (SCL-90-R score 0.85 vs. 0.45, p = 0.001). We could demonstrate that FtM primarily reflect the psychopathological profile of biological males rather than that of biological females (r = 0.945), while MtF showed a slightly higher profile similarity with biological females than with biological males (r = 0.698 vs. r = 0.685).

Conclusion

Our findings suggest that phenotypic sex matched controls are potentially more appropriate for comparison with the psychopathology of transsexual patients than are genetic sex matched controls.     

What many transgender activists don't want you to know: and why you should know it anyway

Currently the predominant cultural understanding of male-to-female transsexualism is that all male-to-female (MtF) transsexuals are, essentially, women trapped in men's bodies. This understanding has little scientific basis, however, and is inconsistent with clinical observations. Ray Blanchard has shown that there are two distinct subtypes of MtF transsexuals. Members of one subtype, homosexual transsexuals, are best understood as a type of homosexual male. The other subtype, autogynephilic transsexuals, are motivated by the erotic desire to become women. The persistence of the predominant cultural understanding, while explicable, is damaging to science and to many transsexuals.     

The biology of human psychosexual differentiation

Most attempts to identify biological underpinnings of gender identity and sexual orientation in humans have investigated effects of sex steroids, so pivotal in the differentiation of the genitalia, showing strong parallels between animals and the human. The information on humans is derived from the so-called 'experiments of nature', clinical entities with a lesser-than-normal androgen exposure in XY subjects and a higher than normal androgen exposure in XX subjects. Prenatal androgenization appears to predispose to a male gender identity development, but apparently not decisively since 40-50% of 46,XY intersexed children with a history of prenatal androgen exposure do not develop a male gender identity. Obviously, male-to-female transsexuals, with a normal androgen exposure prenatally (there is no serious evidence to the contrary) develop a female gender identity, through unknown biological mechanisms apparently overriding the effects of prenatal androgens. The latest studies in 46, XX subjects exposed to prenatal androgens show that prenatal androgenization of 46,XX fetuses leads to marked masculinization of later gender-related behavior but does not lead to gender confusion/dysphoria. The example of female-to-male transsexuals, without evidence of prenatal androgen exposure, indicates that a male gender identity can develop without a significant androgen stimulus. So we are far away from any comprehensive understanding of hormonal imprinting on gender identity formation. Brain studies in homosexuals have not held up in replication studies or are in need of replication in transsexuals. Genetic studies and the fraternal birth order hypothesis provide indications of familial clustering of homosexuality but in many homosexuals these genetic patterns cannot be identified. The biological explanations advanced for the birth order hypothesis lack any experimental support.     

Upregulation of cystic fibrosis transmembrane conductance regulator expression by oestrogen and Bak Foong Pill in mouse uteri

Although cystic fibrosis transmembrane conductance regulator (CFTR) has been shown to be expressed in the female reproductive tract, its functional role in the uterus is not fully understood. The present study investigated a possible physiological role of CFTR by comparing the effects of 17beta-oestradiol and Bak Foong Pill (BFP), an over-the-counter Chinese medicine used for centuries for the treatment of various gynaecological disorders, on uterus size and the expression of CFTR in the uterus of ovariectomised mice using RT-PCR. Treatment of ovariectomised mice with 17beta-oestradiol (0.2 mg/kg, p.o.) for 12 days caused a significant increase in uterine wet weight compared to vehicle. However, treatment with BFP (3 g/kg, p.o.) for the same period failed to increase uterine wet weight, indicating a lack of direct oestrogen-like activity of BFP. Analysis of CFTR mRNA expression in the harvested uteri using RT-PCR showed that both 17beta-oestradiol and BFP induced an increase in CFTR mRNA expression in mouse uteri compared to levels observed in vehicle-treated animals. These results suggest that CFTR can be upregulated by oestrogen and BFP, however, the effect exerted by BFP does not seem to be mediated by direct oestrogen-like activity. Regulation of CFTR expression by both oestrogen and gynaecological medication BFP indicates an important role of CFTR in reproductive functions.     

Effects of 17beta-oestradiol or oestrous stage-specific cow serum on the ability of bovine oviductal epithelial cell monolayers to prolong the viability of bull spermatozoa

The effect of 17beta-oestradiol and oestrous stage-specific cow serum on bovine oviductal epithelial cell monolayers to extend the viability of co-cultured bull spermatozoa was examined. Monolayers of cells from ampullary and isthmic segments were pre-treated with medium containing either oestrous cow serum, luteal-phase cow serum, 1 microg/ml 17beta-oestradiol + foetal bovine serum or foetal bovine serum alone (control) before the addition of motile frozen/thawed spermatozoa. Motility was visually assessed throughout a 48 h co-incubation period, while fertilising ability of spermatozoa was evaluated by adding in vitro matured bovine oocytes. Pre-treatment with 17beta-oestradiol or oestrous cow serum resulted in a higher percentage of motile spermatozoa after 18 h in isthmic and after 36 h in ampullary cultures compared with the control, but pre-treatment did not affect fertilisation rates. Only at 42 h in ampullary cultures was motility higher in luteal serum pre-treated cultures compared to the control. Motility was also assessed in medium conditioned by pre-treated monolayers. Pre-treatment with 17beta-oestradiol enhanced the ability of conditioned medium to prolong motility and medium conditioned with oestrous cow serum was superior to medium conditioned by luteal-phase serum at maintaining motility. In conclusion, the ability of oviductal epithelium to prolong the motility of spermatozoa is enhanced by 17beta-oestradiol.