Microplate solid-phase radioimmunoassay for rat prolactin

A rat prolactin solid-phase radioimmunoassay has been developed that uses 96-well microtiter plates with removable wells to which the antibody is firmly adsorbed, resulting in a solid-phase antibody. Antigen as either reference or unknown competes with radioactivity labeled antigen for binding sites on the solid-phase antibody. After immunoreaction, free antigen is removed by washing the wells with phosphosaline solution. The solid-phase antibody-antigen complex is counted for quantitation with data reduction methods currently used in routine radioimmunoassay procedures. This microplate solid-phase radioimmunoassay has several advantages over conventional methods without sacrificing specificity, sensitivity, or accuracy. This method is rapid, compact, economical, easily automated, and could be readily established in other laboratories.

Relationship between pubertal timing and body size in underfed male rats

A direct connection has been proposed between body size and sexual maturation by the critical body weight and critical body fat hypotheses. To test these theories in male rats, we compared the degree of sexual maturation in animals with reduced growth rate due to undernutrition with that in weight-matched but normally fed rats. Underfed rats had significantly larger prostate, seminal vesicle, and testis weights than the weight-matched normally fed controls at the three time points studied: the early pubertal period (approximate time of onset of rising serum testosterone), late pubertal period (approximate time of appearance of mature spermatids), and young adult period. At the first time point, testes of underfed rats, but not those of normally fed, weight-matched controls, showed mature step 19 spermatids, and serum testosterone was significantly higher in the underfed animals. At all time points, serum LH levels were similar in both groups, while serum FSH levels were significantly lower in the underfed rats at all points. The Lee index, an index of fatness, was significantly lower in the underfed rats. The current study indicates that underfed rats are more sexually mature than normally fed controls of the same weight despite having a lower percentage of body fat. These findings do not support the critical body weight or critical body fat hypotheses of puberty in male rats.

Low serum thyroxine and high serum triiodothyronine in nephrotic rats: etiology and implications for bioavailability of protein-bound hormone

Traditionally, it has been thought that the bioavailable fraction of circulating serum hormones, i.e. that which is available for cellular uptake and is physiologically active, is limited to the free (nonprotein bound) hormone. However, recent evidence, based on acute organ uptake of labeled hormone, suggests that the amount of hormone which is bioavailable in vivo may exceed that which is calculated to be free in vitro. To explore the bioavailability of circulating protein-bound thyroid hormones under steady state conditions in vivo, we altered serum thyroid hormone-binding proteins in rats by inducing nephrotic syndrome with puromycin aminonucleoside. Nephrotic rats (serum albumin, 1.1 g/dl) were found to have a marked reduction in serum T4 [2.1 +/- 0.2 (SEM) vs. 6.5 +/- 0.3 microgram/dl; P less than 0.01] and an elevation of serum T3 [141 +/- 8 vs. 51 +/- 2 ng/dl; P less than 0.01]. Estimated T4 production rate was normal in nephrotic rats, and the 3- to 4-fold increase in T4 MCR appeared to account for the marked reduction in serum T4. By contrast, increased serum T3 levels in nephrotic rats reflected both a reduction (55%) in T3 MCR and an increased rate of peripheral conversion of T4 to T3. A circulating inhibitor of T4 binding to serum proteins appeared to be present in nephrotic rats. The changes in the various serum components of thyroid hormone [T4-binding prealbumin (TBPA)-bound, albumin-bound, free] produced by nephrotic syndrome were compared with the corresponding changes in indices of thyroid hormone bioavailability (MCR, urinary excretion, hepatic content, TSH suppression, single pass extraction by liver). These comparisons suggested that nephrotic syndrome results in increased bioavailability of circulating T4 and decreased bioavailability of circulating T3. The bioavailable fraction of circulating T3 in vivo seemed to include both free T3 and that which is albumin bound in vitro. The bioavailable fraction of circulating T4 resembled free T4 more than non-TBPA-bound T4 (= albumin bound + free), although a nephrosis-induced increase in bioavailability of TBPA-bound T4 was also possible. We conclude that nephrotic rats have low serum T4, which is related to accelerated T4 clearance, and high serum T3, which is related both to decreased T3 clearance and increased peripheral conversion of T4 to T3. Under steady state conditions in vivo, bioavailable circulating T3 appears to include both free T3 and the T3 that is bound to albumin in vitro.

Growth and reproductive adaptation in male rats with chronic protein deficiency

In previous studies, male rats fed a low-protein diet beginning at weaning were found to have impaired sexual development through age 11 weeks when compared to food-restricted, weight-matched controls fed a diet with normal protein content. To determine whether male rats show long-term adaptation of the reproductive axis to low-protein feeding, we assessed sexual maturation and growth in rats fed a low protein (9%) diet from weaning until sacrifice at various points in time between ages 79 and 185 days. After age 80 days, there was no difference in reproductive organ weights (prostate, seminal vesicles, testis) or serum hormone levels (luteinizing hormone, follicle stimulating hormone, testosterone) between protein-deficient animals and food-restricted weight-matched controls given a normal diet. In addition, there was no difference between protein-deficient animals and controls in indices of linear growth (naso-anal and tail length) or fatness (Lee index). We conclude that both growth and reproductive function of male rats show adaptation to long term feeding of a low-protein diet.

Testicular dysfunction in untreated Hodgkin's disease

Gonadal function was examined in 19 young men with Hodgkin's disease before therapy and compared with that of 11 men with other malignancies, 13 men with primary testicular failure, and 19 normal men of similar age. Total (p less than 0.01) and free (p less than 0.05) testosterone levels were decreased in Hodgkin's disease. In those with advanced (stage III + IV) and symptomatic (B), Hodgkin's disease serum testosterone levels were indistinguishable from those in primary testicular failure, yet serum levels of luteinizing hormone were normal. Moreover, the acute response of serum testosterone to exogenous human chorionic gonadotropin (HCG) was significantly greater in Hodgkin's disease than in primary testicular failure (p less than 0.03). These data and the finding that basal serum follicle-stimulating hormone levels are significantly lower than normal in Hodgkin's disease (p less than 0.05) suggest that the cause of pretreatment hypogonadism in Hodgkin's disease is not simple primary testicular failure. Total sperm count was decreased in 40 percent of men with Hodgkin's disease but in none of the men with other malignancies (p less than 0.05), suggesting specific seminiferous tubular dysfunction in Hodgkin's disease. However, motility was abnormal in 69 percent of men with Hodgkin's disease and 60 percent of those with other malignancies, suggesting that this is a nonspecific effect of cancer. Serum prolactin levels were significantly higher than normal in Hodgkin's disease (p less than 0.05) but not in other malignancies. Our findings suggests that the cause of testicular dysfunction that is present before treatment of Hodgkin's disease is complex, perhaps involving both pituitary and gonadal abnormalities.

Testicular reserve of testosterone precursors in primary testicular failure

To explore the abnormal steroidogenesis in subjects with primary testicular failure, we measured serum levels of testosterone (T) and its precursors androstenedione (delta 4A) and 17-hydroxyprogesterone (17-OHP) in the basal state and after stimulation by human chorionic gonadotropin (hCG) for 4 hours (acute reserve) or 72 hours (chronic reserve). Subjects with primary testicular failure had decreased mean basal serum T, decreased mean chronic T reserve, and absent mean acute T reserve. In contrast, these subjects had normal mean basal serum 17-OHP and delta 4A, normal chronic 17-OHP reserve, and non-zero mean acute 17-OHP and delta 4A reserve, although mean chronic delta 4A reserve was reduced. Heterogeneity of biochemical abnormalities depending on the etiology of testicular failure was apparent. In primary testicular failure, the testicular reserves of the T precursors 17-OHP and delta 4A are better maintained than is the reserve of T itself, raising the possibility that this disorder might be associated with biochemical blocks in conversion of T precursors to T.

Pituitary-testicular function in protein-deficient rats. Follicle-stimulating hormone hyperresponse to castration and supersensitivity of gonadotropin secretion to androgen negative feedback

Previous studies have shown that weanling male rats fed a low protein diet ad libitum develop hypogonadotropic hypogonadism. Two unusual features of this state were 1) subnormal serum FSH in noncastrate rats but not in castrate rats, suggesting that FSH was being suppressed by a testicular factor, and 2) serum FSH increases after castration that were greater in protein-deficient rats than in controls. In the current study, protein-deficient rats showed FSH hyperresponse to castration, compared to either ad libitum or pair-fed controls, after periods of low protein feeding from 1-8 weeks and periods of castration from 1-8 weeks. FSH hyperresponse to castration was rapidly induced after the start of low protein feeding and was present whether castration was performed before or after low protein feeding was begun. In none of these circumstances did protein-deficient rats show LH hyperresponse to castration. Inhibin production of Sertoli cell cultures prepared from protein-deficient rats was less (P less than 0.02) than in ad libitum or pair-fed controls, suggesting that inhibin overproduction was not the cause of subnormal serum FSH in noncastrate protein-deficient rats. However, castrated rats fed a low protein diet were more sensitive to the negative feedback effects of testosterone on gonadotropin secretion than were ad libitum or pair-fed controls. We conclude that low serum gonadotropins in protein-deficient male rats may be related to hypersensitivity of these animals to the negative feedback effects of testosterone on gonadotropin secretion. In addition, FSH hyperresponse to castration, without corresponding LH hyperresponse, seems to be typical of protein deficiency, suggesting that protein deficiency may be a useful model for exploring the differential control of gonadotropin secretion.

Methotrexate levels in the interstitial space and seminiferous tubule of rat testis

The ability of methotrexate (MTX) to pass from the blood into the interstitial space and seminiferous tubule of the rat was investigated using testicular micropuncture. MTX was administered to anesthetized adult Wister rats via a femoral vein cannula. Constant plasma levels of MTX were achieved by giving a priming dose followed by a constant infusion of 1, 10, or 100 mg/kg/hr with 6 to 27 rats studied at each dose. Blood (via a jugular vein cannula), testicular interstitial fluid, and seminiferous tubule fluid (via direct micropuncture) were periodically sampled during the 4 hr of drug infusion. Under steady-state conditions, when compared to corresponding plasma values, MTX levels were 2- to 4-fold lower in the testicular interstitial fluid and 18- to 50-fold lower in the seminiferous tubule. These results indicate that, in the rat, a significant blood-testis barrier to MTX exists at the tubular but probably not at the capillary-interstitial level. If these results can be extrapolated to humans, they do not provide a pharmacological explantation for the frequent occurrence of leukemic relapse in the interstitium of the testes in boys with acute lymphocytic leukemia.

The effects of pyridoxine on pituitary hormone secretion in amenorrhea-galactorrhea syndromes

Six patients with amenorrhea, five of whom had galactorrhea and elevated PRL levels, were evaluated on a metabolic ward. All had normal sella tomograms, normal thyroid functions, and routine laboratory evaluations. None of the patients had taken any medication in the previous 6 months. On alternate days, five patients received 500 microgram of TRH iv with the measurement of PRL, TSH, FSh, LH, and hGH; 500 mg L-dopa orally with the measurement of PRL, FSH, and LH; a bolus infusion of 300 mg pyridoxine (B6) with measurement of PRL, hGH, TSH, FSH, and LH; and 25 mg chlorpromazine (CPZ) im with the measurement of PRL, LH, and FSH. The patients were then discharged on 600 mg oral pyridoxine/day and were readmitted for a repeat of the complete protocol 21 days later. The patients were continued on 600 mg oral pyridoxine for 3-4 months with monthly evaluations of serum PRL, LH, and FSH levels. These evaluations continued for 3 months after discontinuing pyridoxine. There was no demonstrable change in serum PRL after acute or chronic B6 therapy, mor was there a significant change in the response of PRL to CPZ, L-dopa, or TRH. The mean basal PRL was 97.5 +/- 9.7 ng/ml and after 3-4 months of oral pyridoxine was 97.1 +/- 14.8. In addition, there was no significant change in LH or FSH levels in response to acute or chronic B6, TRH, L-dopa, or CPZ. Neither acute B6 infusion nor chronic B6 therapy had any effect on TSH or the TSH response to TRH. Finally, acute B6 infusion had no effect on hGH levels and there were no paradoxical hGH responses to TRH. Two patients began having regular menses while on chronic pyridoxine. Their hormonal responses did not differ from those of the group, however.

The antiandrogenic effects of delta 1-testolactone (Teslac) in vivo in rats and in vitro in human cultured fibroblasts, rat mammary carcinoma cells, and rat prostate cytosol

The antiandrogenic properties of delta 1-testolactone (17 alpha-oxa-D-homo-1,4-androstane-3,17-dione; Teslac) were investigated in vivo and in vitro. Teslac (75 mg/day for 7 days) inhibited the rise in ventral prostate weight induced by testosterone (T) (P less than 0.001), dihydrotestosterone (DHT) (P less than 0.05), and a combination of T plus 17 beta-estradiol (E2) (P less than 0.01) in immature castrate rats. Similar effects were seen on the seminal vesicles after T and T plus E2 (P less than 0.001). Teslac also decreased prostate and seminal vesicle weights in intact immature rats. The effects of Teslac were dose and time dependent. Teslac did not change the concentration of serum T or DHT. However, Teslac inhibited DHT binding to the androgen receptor (Ki = 2.5 +/- 0.8 X 10(-7) M) in cytosol of the rat prostate. Teslac also inhibited DHT binding to the androgen receptor in cultured human prepuce fibroblasts and cultured rat mammary tumor cells (Ki = 1.9 +/- 0.3 X 10(-5) M). The results indicate that Teslac, in addition to its antiaromatase activity, is an antiandrogen by virtue of its interaction with the androgen receptor.

Cushing's disease presenting as amenorrhoea with hyperprolactinaemia: report of two cases

Two patients with Cushing's disease first presented with amenorrhoea, hyperprolactinaemia, and normal tomograms of the sella turcica. Both women underwent trans-sphenoidal removal of a pituitary microadenoma resulting in a decreased serum prolactin concentration in both, and cessation of galactorrhoea and return of menses in one of them. One woman became ACTH deficient while the other has persistent Cushing's disease. A survey of the literature on Cushing's disease and prolactinomas shows the association to be uncommon. A likely mechanism is secretion of both hormones by the microadenomas. These two patients illustrate the need for screening other pituitary hormone function in patients with hyperprolactinaemia.

Effects of delta 1-testolactone on the pituitary-testicular axis in oligospermic men

Ten men with idiopathic oligospermia were treated with delta 1-testolactone (Teslac), a potent inhibitor of conversion of androgens to estrogens. Teslac therapy caused a fall in serum estradiol and estrone levels of 34% (P less than 0.01) and 41% (P less than 0.01), respectively, and a rise in serum testosterone and androstenedione of 47% (P less than 0.02) and 70% (P less than 0.01), respectively. The testosterone-estradiol ratio increased by 126% (23.5 +/- 2.5 x 10(-1) to 45.2 +/- 5.0 x 10(-1); P less than 0.01) and the androstenedione:estrone ratio increased 231% (4.7 +/- 0.6 x 10(-1) to 12.9 +/- 2.0 x 10(-1); P less than 0.01). Basal and LRH-stimulated serum gonadotropin levels were unaffected by these changes. Sperm density rose from 10.8 +/- 2.5 to 19.8 +/- 4.7 x 10(6)/ml (P less than 0.01) and total sperm count from 26.8 +/- 6.5 to 60.6 +/- 14.3 x 10(6) (P less than 0.001). There was no significant change in motility or semen volume. Three of the wives became pregnant. There were no adverse effects of Teslac administration. These data suggest that Teslac may be an effective treatment for men with idiopathic oligospermia. Though the data do not clearly elucidate the mechanism of this effect, they are consistent with the possibility that Teslac's lowering of estrogen levels may have been responsible for the improvement in spermatogenesis. The findings also suggest that moderate increases in the circulating androgen-estrogen ratio do not affect gonadotropin output in men.

Marihuana inhibits dihydrotestosterone binding to the androgen receptor

Marihuana and its constitutents delta 9-tetrahydrocannabinol (delta 9-THC) and cannabinol (CBN) were tested for their ability to interact with the androgen receptor in rat prostate cytosol. Smoked marihuana condensate, delta 9-THC, and CBN inhibit specific binding of dihydrotestosterone (DHT) to the androgen receptor with a dissociatin constant of the inhibitors (Li) of 2.1-5.8 X 10(-7)M. in addition, other metabolites of delta 9-THC were also androgen antagonists. This data suggests that the anti-androgenic effects associated with marihuana use results, at least in part, from inhibition of androgen action at the receptor level.

Leydig cell function in idiopathic oligospermia

To assess Leydig cell function in men with idiopathic oligospermia, serum levels of testosterone and 17-hydroxyprogesterone were measured before and after the administration of human chorionic gonadotopin (hCG) to men with oligospermia (< 20 x 10(6) sperm/ml). Serum testosterone and 17-hydroxyprogesterone levels, both basally and after 2 or 72 hours of hCG stimulation of Leydig cell output, were the same in the oligospermic and control groups, although basal serum testosterone levels correlated directly with sperm density (r = 0.34; P < 0.05). The basal serum level of luteinizing hormone (LH) was slightly but significantly higher in the oligospermic group than in the control group (12.0 +/- 1.0 [SE] mIU/ml versus 9.5 +/- 0.5; P < 0.05), as was the LH:testosterone ratio (2.45 +/- 0.20 versus 1.74 +/- 0.20; P < 0.02). The combination of slightly elevated serum LH levels with unchanged basal serum levels of gonadal steroids suggests that men with idiopathic oligospermia have a mild, compensated Leydig cell defect. The mildness of this defect is reflected by the ability of maximal gonadotropic stimulation to increase androgen output.

Murine thymic androgen receptors

Studies in mice indicate that sex hormones influence the immune system. In general females are more immunocompetent than males and the administration of androgens can suppress antibody formation in females. New Zealand Black (NZB) mice manifest a lack of sex difference in the production of certain autoantibodies and the failure of androgen administration to suppress these antibody levels. To further analyze this phenomenon, androgen receptors were studies in the thymus of NZB and a non-autoimmune strain (C57Bl/6). Specific thymic androgen receptors were found in both NZB and C57Bl/6 mice. The dissociation constant and concentration of specific dihydrotestosterone receptors was determined in thymic cytosol by Scatchard plot analysis. There were no substantial differences in the binding parameters between sexes and between strains. In conclusion, both autoimmune and control strains have similar high affinity thymic androgen receptors. Therefore, the immune androgen insensitivity observed in NZB mice is not the result of a lack of high affinity thymic androgen receptors.

Relative binding of testosterone and estradiol to testosterone-estradiol-binding globulin

The binding of estradiol (E2) and testosterone (T) to testosterone-estradiol-binding globulin (TeBG) was studied in vivo at 37 C by three independent methods: equilibrium dialysis, steady state polyacrylamide gel electrophoresis, and TeBG-ligand dissociation kinetics. Equilibrium dialysis was performed at 37 C with the dialysate containing human serum albumin in amounts equivalent to that of the plasma dialysand. Scatchard analysis indicated that under these conditions E2 does not measurably bind to TeBG, while T has a Kd of 3.7 X 10(-10) M. Similarly, Scatchard-type analysis of E2 binding to TeBG in steady state polyacryalmide gel electrophoresis at 37 C revealed no high affinity saturable binding, while dihydrotestosterone was bound with a Kd of 2.7 X 10(-10) M. Examination of the dissociation kinetics of T and E2 ffrom TeBG revealed that the mean (+/-SD) T1/2 of dissociation of T from plasma at 37 C (10.8 +/- 2.4 min) was significantly shortened to 3.5 +/- 0.4 min by saturation of plasma with dihydrotestosterone (P less than 0.01), whereas that of E2 (8.9 +/- 1.4 min) was not changed (9.6 +/- 3.0 min). These data suggest that TeBG is not an important binder of plasma E2 at physiological temperatures and explain the observation that in diseases characterized by high TeBG levels, such as hyperthyroidism and liver disease, the MCR and free E2 levels have generally been normal.

The hypothalamic-pituitary-testicular axis in thyrotoxicosis

The hypothalamic-pituitary-testicular axis was evaluated in seven men with thyrotoxicosis due to Graves' disease. Loss of libido and decreased potency were present in 71% and 56%, respectively. All patients had normal testicular volume (25 ml in all) and gynecomastia was detected in two of seven patients. Total sperm counts were less than 40 million in four of the five men tested. There was an inverse correlation between basal serum 17 beta-estradiol (E2) levels and total sperm count (r = -0.87; P less than 0.05). Mean (+/- SE) total testosterone (T) and E2 levels (1008 +/- 104 ng/100 ml and 104 +/- 16 pg/ml) were significantly higher than in normal men (P less than 0.05). Free T (13.6 +/- 2.4 ng/100 ml) was indistinguishable from normal (15.3 +/- 1.5 ng/100 ml). The mean (+/- SE) response of serum T to hCG administration was blunted (80 +/- 40%) compared to controls (193 +/- 19%; P less than 0.02). Basal plasma LH levels (15.5 +/- 1.5 mIU/ml) were significantly higher (P less than 0.05) than in normal men (9.1 +/- 0.6 mIU/ml) and hyperresponded to 100 microgram LRH iv in five of seven patients. Basal plasma FSH levels and the FSH response to LRH were normal. These results suggest that men with hyperthyroidism have 1) partial Leydig cell failure, 2) impairment of spermatogenesis, and 3) blunting of the feedback effects of E2.

Adrenal suppression after short-term corticosteroid therapy

Adrenal function was evaluated in fourteen cancer patients receiving chemotherapy which included short-term high-dose courses of prednisone. 90 min corticotropin stimulation tests were performed before therapy and 1, 2, 4, and 7 days after steroids were discontinued. Responses were evaluated by standard criteria of adrenal function and by measurement of the intergrated cortisol response to corticotropin over 90 min. Thirteen of fourteen patients had suppressed adrenal function for at least 24 h. Although in most patients adrenal function had returned to normal between day 2 and 4, in five patients it remained suppressed for 7 days or more. Suppression did not correlate with either steroid dose or duration of therapy. Four of five patients receiving only 5 days' therapy showed evidence of adrenal suppression. Although overt clinical adrenal insufficiency after steroid administration is rare, these results indicate that adrenal function is suppressed more regularly after short-term high-dose steroid therapy than has been appreciated.

Hypoandrogenism and abnormal regulation of gonadotropin secretion in rats fed a low protein diet

The function of the hypothalamic-pituitary-testicular axis was evaluated in rats fed a low protein diet for 4 weeks beginning at 21 days of age. Compared to control, the low protein group had decreased seminal vesicle and prostate weights as well as decreased testicular testosterone output in vitro, although serum testosterone was not different. The low protein group showed no consistent alterations in serum LH (basal, post-LHRH, and postcastration) compared to control although serum FSH (basal and post-LHRH) was lower in the low protein group. Despite this lower basal FSH, the low protein group had supranormal serum FSH after castration. Seminiferous tubule diameter and testicular histology were normal in the low protein group although testicular androgen-binding protein was absent. Testicular androgen-binding protein was also undetectable in a modestly food-restricted control group which had normal testicular size, testicular histology, androgen output, and serum FSH. This finding suggests that loss of testicular androgen-binding protein may be a sensitive sign of undernutrition. We conclude that rats fed a low protein diet have hypoandrogenism, normal testicular histology, and supranormal FSH after castration despite subnormal basal FSH. The latter combination suggests overproduction of an FSH inhibitor of testicular origin.