Radioimmunoassay of serum medroxyprogesterone acetate (Provera) in women following oral and intravaginal administration.

A radioimmunoassay (RIA) method for measuring medroxyprogesterone acetate (MPA, Provera) in serum has been developed utilizing benzene:iso-octane extraction, 3H-MPA to assess procedural losses, goat anti-MPA-3-(0-carboxymethyl) oxime-bovine serum albumin serum and dextran-coated charcoal separation. Control serum blanks were undetectable, 200 pg/ml of MPA was measurable with a high reliability, and intra- and interassay coefficients of variation were 6 and 13 percent, respectively. MPA added to control serum was quantitatively recovered. Serum MPA levels measured in 2 women after ingestion of 10 mg MPA rose to 3.4 to 4.4 ng/ml within 1 to 4 hours after oral intake and fell rapidly thereafter to 0.3 to 0.6 ng/ml within 24 hours. Insertion of Silastic intra-vaginal rings (IVRs), containing 100 or 200 mg of MPA, into 4 women for periods of 3 weeks resulted in a rapid rise of serum MPA after insertion, rather stable MPA levels of 0.9 to 1.6 ng/ml while the IVRs were in place, and a rapid decline of serum MPA following IVR removal. Serum estradiol-17beta and progesterone concentrations, measured about 3 times a week in these patients, indicated that ovulation was consistently inhibited. The serum MPA levels observed in this study were approximately 5 times lower than those reported by other investigators using a double-antibody RIA of MPA in unextracted serum.     

Medroxyprogesterone acetate in human serum

Conjugates of medroxyprogesterone acetate (MPA) in human serum are investigated using chromatography and techniques (equilibrium dialysis, gel filtration, and polyacrylamide gel electrophoresis) previously described for studying the binding of MPA. 17 serum samples were obtained from 7 women at various times after the intramuscular injection of 150 mg Depo-Provera. Mean concentration of MPA in the unconjugated fraction of serum was 3.9 mg/ml (range 0.8-10.7 ng/ml); in the conjugated fraction, the value was 2.7 ng/ml (range 0.6-11.4 ng/ml), a mean value of 81.7% (range 18.4-286%) of that in the unconjugated fraction. The conjugate appears to be mainly a glucuronide since solvolysis released only small amounts of MPA. MPA metabolites were also detected in blood. The MPA levels in blood measured by radioimmunoassay were generally lower when serum was extracted with an organic solvent rather than when the assay was carried out directly in the serum. This finding suggests the presence in blood of either MPA in a conjugated form or metabolites interacting with the antiserum which were not extracted by the solvents used. Equilibrium dialysis showed that undiluted plasma bound 85.8% of triated hydrogen-MPA; with increasing dilution of the plasma, the amount of bound triated hydrogen-MPA decreased. The apparent association constant calculated according to the method of Vermeulen and Verdonck was 2.6 x 10 4 1/mol. MPA appeared to be loosely bound to albumin in blood but there was no specific binding protein for the steroid. MPA conversion to the glucuronide may be 1 of the factors regulating the level of the unconjugated but presumably biologically active steroid in blood.     

Biological effects of hormone replacement therapy in relation to serum estradiol levels

OBJECTIVE: Tissues in various parts of the body have different sensitivities to estradiol. However, it is very difficult to measure the serum estradiol levels precisely in women receiving oral conjugated equine estrogen, which is a mixture of estrogens. In the present study, we precisely measured the serum levels of estradiol in postmenopausal women undergoing hormone replacement therapy (HRT), and we clarified the relationships between serum estradiol levels and the effects of HRT on the Kupperman index, bone mineral density (BMD), serum gonadotropin, lipid metabolism and unscheduled bleeding as the clinical endpoints. METHODS: Sixty-eight postmenopausal or bilaterally ovariectomized women, aged 30-64 years, who had been suffering from vasomotor symptoms such as hot flush or atrophy of the vagina were randomly assigned to two groups: one group of 34 patients who received oral administration of 0.625 mg conjugated equine estrogen (CEE, Premarin, Wyeth) and 2.5 mg medroxyprogesterone acetate (MPA, Provera, Upjohn) every other day, and another group of 34 patients who received oral administration of 0.625 mg CEE and 2.5 mg MPA every day. All subjects were re-classified into three groups according to the serum estradiol level after 12 months of treatment: (1) low estradiol group (<15 pg/ml, n = 25); (2) middle estradiol group (> or =15 and <25 pg/ml, n = 27), and (3) high estradiol group (> or =25 pg/ml, n = 16). We examined the relationships between serum estradiol level and the effects of estradiol on the Kupperman index, BMD, serum gonadotropin levels, lipid profile and unscheduled bleeding in these three groups. Results: Results obtained by using our newly developed high-performance liquid chromatography (HPLC)-radioimmunoassay (RIA) system clearly showed that the effects on each tissue in postmenopausal women receiving oral CEE and MPA is closely related to estradiol level. The effects of HRT on BMD, serum gonadotropin levels and lipid profile were shown to be clearly dependent on the serum estradiol levels, while the effect of HRT on the Kupperman index was independent of the serum estradiol level. Furthermore, it was also found that a very low concentration of estradiol (<15 pg/ml) was sufficient to suppress the serum LH and FSH levels and to relieve vasomotor symptoms, and that the minimum concentration of estradiol required to increase BMD was 15 pg/ml. On the other hand, the level of estradiol required to reduce total cholesterol, low density lipoprotein-cholesterol (LDL-C) and apolipoprotein B (Apo B) was found to be more than 25 pg/ml, while the level required to increase high density lipoprotein-cholesterol (HDL-C) and apolipoprotein A1 (Apo A1) was at least 15 pg/ml. The incidence of unscheduled bleeding was also lower in the low estradiol group than in the other estradiol level groups. CONCLUSION: These results suggest that the different clinical endpoints have different response thresholds and thus reflect tissue sensitivity to estradiol levels achieved by HRT.     

Effect of progestins on serum hormones,semen production,and agonistic behavior in the gerenuk (Litocranius walleri walleri)

The use of progestins to suppress endogenous testosterone production to reduce agonistic behavior and prevent semen production was studied in gerenuk. Five male gerenuk (20 months to 3 years of age), housed as a bachelor group, were treated with 3 monthly injections of medroxyprogesterone acetate (MPA; 2.5–20 mg/kg), followed by a melengestrol acetate implant (MGA; 0.3 g/kg) for 2 months. Blood samples collected monthly were assayed for serum testosterone and cortisol using enzyme‐linked immunoassays. Quantitative behavioral data were collected for 30 min 3/week starting 1 month before treatment. Body weight, testes volume, and semen traits were measured before treatment, after MPA treatment, and after MGA treatment. Results showed lower (P<0.05) mean serum testosterone concentrations after MPA (4.34 pg/ml) and MGA (5.02 pg/ml) treatment compared to pre‐treatment values (65.9 pg/ml) in four of five gerenuk. The remaining sub‐adult gerenuk had low testosterone initially (4.9 pg/ml) that did not decrease further with treatment (1.4 and 7.8 pg/ml for MPA and MGA, respectively). Mean serum cortisol concentrations decreased markedly after treatment with MPA (6.0±3.7 ng/ml) and MGA (0.8±0.3 ng/ml). Cortisol concentrations were regained rapidly post‐treatment (42.8±4.8 ng/ml) and were not significantly different from the pre‐treatment value (60.6±12.6 ng/ml; P>0.05). The mean incidence of combined aggressive/dominant behaviors (horning, sparring, supplanting, threat) was not different before and after treatment. Body weight, total numbers of spermatozoa produced per ejaculate, percent motility, and percent normal spermatozoa declined maximally 8 months after treatment. Mean testes volume decreased (P<0.05) after MGA treatment (10.53 cm³vs. 11.96 cm³ pre‐treatment). Elevated hepatic enzymes and bile acids were seen in three of five animals after progestin treatment and anorexia was noted in two males after MGA implant removal, however two of three males had elevated liver enzymes before progestin treatment began. Results show that reducing serum testosterone concentration does not seem to modify agonistic behavior in bachelor gerenuk groups. Zoo Biol 26:245–257, 2007. © 2007 Wiley‐Liss, Inc.     

Detection of pregnancy by radioimmunoassay of a novel pregnancy-specific protein in serum of cows and a profile of serum concentrations during gestation

The development of a double antibody radioimmunoassay for a bovine pregnancy-specific protein (pregnancy-specific protein B; PSPB) is presented. By means of this assay, PSPB could be measured in serum of pregnant cows. Five dairy cows were bled throughout gestation to measure serum levels of PSPB. Serum concentrations (means +/- SE) exceeded 1 ng/ml by 30 days postbreeding and increased gradually through three months (9 +/- 0.6 ng/ml), six months (35 +/- 6 ng/ml), and nine months (150 +/- 75 ng/ml) of gestation. Maximum levels of PSPB (542 +/- 144 ng/ml) were reached two days before parturition and then steadily declined to less than 78 ng/ml by 21 days postpartum. In 21 cows bled daily from 15 through 30 days postbreeding, PSPB could be measured in a few cows before and in most cows by 24 days after breeding. In a commercial herd of 102 beef cows, the assay could detect pregnancy earlier and more accurately than the routine method of rectal palpation. This radioimmunoassay measures a unique antigen that, for the first time, provides a serological method for detecting pregnancy in cows.     

Embryotoxicity of a single dose of medroxyprogesterone acetate (MPA) and maternal serum MPA concentrations in cynomolgus monkey (Macaca fascicularis)

A single dose of MPA (Depo-Provera; Upjohn Co., Kalamazoo, Michigan) was administered intramuscularly to 12 time-mated pregnant cynomolgus monkeys on day 27 (+/- 2) of gestation at 25 mg/kg or at 100 mg/kg. Maternal blood samples were collected immediately prior to MPA injection and then at regular intervals until cesarean section at term (day 152 +/- 3). Infants in both dose groups had external genital abnormalities. Female infants in the low-dose groups had partial or complete labial fusion, prominent median raphe, and clitoral hypertrophy; at high doses (100 mg/kg), the female infants had complete labial fusion and a distinct penile urethra. MPA had an opposite effect on external genitalia of male infants. The penis was short and the scrotal swelling was absent or less conspicuous, and two males had hypospadias. The adrenal glands were significantly smaller (P less than 0.05) in infants of both sexes treated with 100 mg/kg. One of the infants treated with 25 mg/kg of MPA had a muscular ventricular septal defect. Serum concentrations of MPA were determined by radioimmunoassay in eight pregnant monkeys. In the 25 mg/kg group the patterns of MPA profiles in the serum were similar in all four animals. An initial peak occurred at 24-48 hr postinjection (2.7-9.6 ng/ml), followed by a slight decrease at 3 days postinjection (gestational day 30), and then a steady increase to maximum levels of 10-14 ng/ml occurring between gestational days 37 and 50. Serum levels gradually declined to concentrations below 5 ng/ml by midgestation in three of four monkeys. By comparison, both the patterns and magnitude of MPA concentration showed great interanimal variation in the 100 mg/kg group. MPA was present in cord blood at measurable concentrations in infants at both dose groups; the levels ranged from 0.6 to 8.3 ng/ml, corresponding to 40-72% of the maternal concentrations. These results demonstrate that a single injection of MPA during early pregnancy causes selective embryotoxicity in both male and female fetuses. Presence of high levels of MPA in maternal sera during the critical period of genital development can cause specific genital defects; however, the exact mechanism by which MPA causes these paradoxical genital abnormalities is unknown.     

Assay of ethynyloestradiol in human serum and its binding to plasma proteins

A radioimmunoassay for estimating both unconjugated and conjugated ethinyl estradiol (EE) in serum is described, along with a report of levels of EE attained after its administration and the binding of EE in plasma, as determined by this radioimmunoassay. Mean values for concentration of free EE were 38-87 pg/ml, 1-4 hours after administration, and by 24 hours levels in most subjects were below the sensitivity level of this assay, which is less than 25 pg/ml. Conjugated EE concentration in serum was considerably higher, with mean values of 370-770 pg/ml 1-4 hours after ingestion, decreasing slowly to mean values of 285 pg/ml at 8 hours and 100 pg/ml at 24 hours postadministration. Total EE (conjugated plus unconjugated) had a mean half-life of 3.8 hours during the period 2-8 hours after administration and 10.7 hours for the period 8-24 hours postadministration. EE in plasma was shown, by equilibrium dialysis, gel filtration on Sephadex G200, and polyacrylamide gel electrophoresis, to bind only to albumin, and no specific binding of EE occurred. The apparent association constant for the binding of EE to human serum albumin was 1.7 times 10 5 liter per mol.     

Improvement and initial in vivo application of the radioimmunoassay of rat thyrocalcitonin.

Previously we reported a homologous radioimmunoassy for rat thyrocalcitonin (TCT) which was sensitive enough (2--3 ng/ml serum) to measure TCT in thyroid venous blood or thyroid gland extracts but could not detect TCT in peripheral blood even after provocative challenge with iv calcium. In the present study chicken antisera to rat TCT were developed which were sufficiently sensitive (120--240 pg/ml serum) to permit initial evaluation of changes in TCT in rat peripheral blood. The following results were observed: (1) Basal serum TCT in young male Holtzman rats was undetectable, being less than 120--240 pg/ml; (2) induction of marked hypercalcemia by iv calcium increased TCT to approximately 1000--3000 pg/ml within 5 min; (3) thyroid cautery increased TCT to approximately 1000 pg/ml in 5--15 min; (4) calcium gavage (12.2 mg Ca/100 g) produced modest hypercalcemia in 30--60 min and increased serum TCT to approximately 500 pg/ml; (5) injection of isoproterenol raised serum TCT detectably; (6) injection of large doses of gastrin or pentagastrin did not produce detectable increases in TCT 5 or 30 min later. The results show that suitable antisera to rat TCT can be developed in chickens and applied to the measurement, by radioimmunoassay, of elevated circulating levels of TCT in the rat.     

Radioimmunoassay for non-suppressible insulin-like activity.

By immunizing rabbits--tolerant against the bulk of normal human serum proteins--with highly purified non-suppressible insulin-like activity (NSILA-S), an antiserum was obtained which made possible the development of a double-antibody radioimmunoassay. Its sensitivity is about 30 pg NSILA-S per tube or 150 pg NSILA-S/ml. The specificity exceeds that of the bioassay used for comparison which is based in the stimulation by NSILA-S of 125IUDR incorporation into chicken fibroblasts in culture. The radioimmunoassay is sufficiently sensitive and specific to allow direct NSILA-S measurement in serum or plasma samples of humans and experimental animals. In human plasma samples NSILA-S levels, carrying between less than 0.15 and 25 ng/ml , were found to have an average of about 4 ng/ml. In rats higher levels were observed with a mean of 7.7 ng/ml in 4-week-old animals, increasing to about 60 ng/ml in 6-month-old rats. In fasting rats the NSILA-S plasma level is reduced. In acid-treated samples of plasma considerably higher NSILA-S amounts are found.     

Plasma C-type natriuretic peptide levels in healthy children

C-type natriuretic peptide (CNP) is assuming increasing importance in cardiovascular disease, and in adults its plasma levels are related to clinical and functional disease severity. Data are scarce regarding the reference values for CNP in infancy. Aim of this study was to assess the reference intervals for CNP in human healthy newborns and infants. Plasma CNP was measured in 121 healthy children divided into: 41 newborns (age 0-3 days), 24 newborns (4-30 days), 22 infants (1-12 months) and 32 children (1-12 years). A group of 32 healthy adult subjects (age 64 ± 1 years) was also studied. CNP was measured by a specific radioimmunoassay. Between- and within-assay variability resulted ≤ 30 and 20%, respectively and analytical sensitivity 0.77 ± 0.05 pg/tube. Plasma CNP resulted significantly higher in children than in adult subjects (13.6 ± 1.2 pg/ml vs. 7.4 ± 1.0 pg/ml, p=0.030). When the results were analyzed as a function of the age the reference intervals for plasma CNP resulted: 11.6 ± 2.1 pg/ml for newborns (0-3 days), 16.4 ± 3.7 pg/ml for newborns (4-30 days), 15.4 ± 2.7 pg/ml for infants (1-12 months), 13.6 ± 2.3 pg/ml for children (1-12 years) [p=0.01 newborns (4-30 days) vs. adults; p=0.03 infants (1-12 months) vs. adults]. CNP showed the highest concentrations after 12h of life with a peak between 4 and 5 days of life and with a progressive decline afterwards. According to these data at least five different reference intervals for CNP determinations should be used. These observations may be helpful for future clinical application of CNP in human children.     

Peripartal changes of estrone, progesterone and prostaglandin in the water buffalo

The peripheral blood plasma concentration of estrone, progesterone and 15-keto-13, 14-dihydroprostaglandin F2alpha (PGF2alpha metabolite) were determined by radioimmunoassay techniques during the peripartal period in 5 buffalo cows belonging to a river type breed. Estrone levels started to increase from below 200 pg/ml about 15 days prior to parturition, and reached high concentrations (400-750 pg/ml) during the last 5 days of pregnancy. The estrone concentration decreased to baseline levels after delivery. The concentration of progesterone fluctuated between 800 and 2000 pg/ml until 15 days before calving and showed a gradual increase during the last 15 days of pregnancy. The progesterone levels declined abruptly on the day of calving and remained below 100 pg/ml for up to 60 days post-partum. Increased levels of the prostaglandin metabolite were recorded from 15 days prior to parturition with further increases occurring during the last 3 days of pregnancy. PGF2alpha metabolite levels declined gradually after parturition, reaching base line levels 15-20 days after calving.     

Serum profiles of luteinizing hormone,progesterone and total estrogens during the canine estrous cycle

Serum levels of LH, total estrogen and progesterone were measured daily by radioimmunoassay during proestrus, estrus and early diestrus in five beagle bitches. Occurrence of the LH peak relative to the onset of estrus was quite variable ranging from 3 days before to 7 days after the onset of estrus. Serum LH levels were elevated for 3 days with a peak value of 25 ± 2 ng/ml reached 2.4 days after the start of estrus. LH levels were ≤ 2 ng/ml when measured at other times during the estrous cycle. Estrogen titers ranged from 84 ± 39 pg/ml at 9 days before the LH peak to 175 ± 15 pg/ml coincident with the LH peak. A broad estrogen peak was evident beginning 5 days before and continuing for 5 days after the LH peak. An estrogen surge was seen in 4 of 5 dogs immediately preceding or coincident with the LH peak suggesting that LH release in the bitch is triggered by a sharp elevation in estrogen levels. Serum progesterone levels rose from ≤ 5 ng/ml before the LH peak to 46 ± 6 ng/ml 6 days afterwards.     

A role for aromatizable androgens in female rat puberty

The function that aromatizable androgens may have in female puberty is unclear. The present experiments were undertaken to examine, using a quantitative approach, the role that physiological levels of these androgens may play in determining the timing of vaginal opening and first ovulation in female rats. Serum androstenedione (delta 4) levels increased markedly between Postnatal Days 4 and 8, remained elevated through Day 16, and declined thereafter to remain at about 100 pg/ml throughout juvenile development (Days 20-32). Serum testosterone (T) also increased, though less prominently after Postnatal Day 4. Maximal values were found at Day 12 (about 150 pg/ml); thereafter, T levels decreased to intermediate values (about 100 pg/ml), which were maintained during juvenile days. Serum dehydroepiandrosterone (DHA) remained undetectable throughout prepubertal development. At puberty, serum delta 4 increased 2.5-fold, but only at the time of the preovulatory luteinizing hormone (LH) surge. In contrast, T levels increased significantly 2-fold on the early proestrous-2 phase of puberty, 3.5-fold on the morning of first proestrus, and 9-fold at the time of the LH surge. Serum DHA remained undetectable. Implantation of Silastic capsules containing T at 2 or 6 mg/ml oil into juvenile 28-day-old rats resulted in serum T levels similar to those found on early proestrous 2 (about 150-180 pg/ml) and at 1300 h of first proestrus (ca. 300-400 pg/ml), respectively. Both treatments induced precocious vaginal opening, but failed to advance first ovulation. About 50% of the T-implanted rats had ambiguous estrous-type vaginal cytology preceding the day of first diestrus, and failed to show corpora lutea at this time.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dehydroepiandrosterone therapy in men with angiographically verified coronary heart disease: the effects on plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (tPA) and fibrinogen plasma concentrations

INTRODUCTION: The aim of this study was to analyze the influence of DHEA therapy on fibrinogen, plasminogen activator inhibitor-1 (PAI-1) and tissue plasminogen activator (tPA) plasma concentrations in men with decreased serum DHEA-S levels and angiographically verified coronary heart disease (CHD). MATERIAL AND METHODS: The study included thirty men aged 41-60 years (mean age 52 +/- 0.90 yr) with serum DHEA-S concentration < 2000 mg/l, who were randomized into a double-blind, placebo-controlled, cross-over trial. Subjects completed the 80 days study of 40 days of 150 mg oral DHEA daily or placebo, and next groups were changed after 30 days of wash-out. Fasting early morning blood samples were obtained at baseline and after each treatment to determine serum hormones levels (testosterone, DHEA-S, LH, FSH and estradiol) and also fibrinogen, plasminogen activator inhibitor-1 (PAI-1) and tissue plasminogen activator (tPA) plasma concentrations. RESULTS: Administration of DHEA was associated with 4.5-fold increase in DHEA-S levels. Estrogen levels significantly increased after DHEA from 22.1 +/- 0.7 pg/ml to 26.4 +/- 1.6 pg/l (mean +/- SEM; p < 0.05), while testosterone levels did not changed. Fibrinogen concentrations significantly decreased in DHEA group from 4.5 +/- 0.3 g/l to 3.83 +/- 0.2 g/l (p < 0.05 vs. placebo). Changes of tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) were not statistical significant (respectively: 8.37 +/- 0.4 ng/ml vs. 8.93 +/- 0.5 ng/ml and 82.3 +/- 6.3 ng/ml vs. 92.7 +/- 9.1 ng/ml (mean +/- SEM; NS vs. placebo). Tolerance of the treatment was good and no adverse effects were observed. CONCLUSIONS: DHEA therapy in dose of 150 mg daily during 40 days in men with DHEAS levels < 2000 mg/l and angiographically verified coronary heart disease (CHD) was connected with significant decreasing of fibrinogen concentration and increasing of estradiol levels, and did not influence on plasminogen activator inhibitor-1 (PAI-1) and tissue plasminogen activator (tPA) plasma concentrations.     

Oxytocin levels during breast-feeding in established lactation

Serial blood samples were taken from eight lactating women while they were nursing their babies 1–4 months postpartum, and from four lactating controls while they were not nursing. The plasma was assayed for oxytocin by radioimmunoassay after extraction with activated Vycor glass powder. In the suckling mothers mean plasma oxytocin rose from 5.4 pg/ml before nursing to 13.0 pg/ml during nursing. Oxytocin levels changed rapidly from minute to minute, with individual peaks as high as 54 pg/ml. Oxytocin levels in the control mothers averaged 4.4 pg/ml.     

Seasonal changes in reproductive function of the rainbow trout (Salmo gairdneri)

The sequential changes in serum oestradiol 17β (measured by specific radioimmunoassay), vitellogenin (measured by phosphoprotein phosphorus content) and total calcium (measured by fluorimetry) in male and female rainbow trout under a simulated natural photoperiod cycle were investigated. Resting levels of 130 pg/ml serum oestradiol in both male and female fish were found in April and May. In the female, levels reached a peak of 4800 pg/ml in October, and almost returned to resting levels just prior to spawning in mid-January. No significant change from resting levels was seen in the male fish.
In both male and female fish levels of 25 μg/ml serum phosphoprotein phosphorus and 10–14 mg % total serum calcium were found from April to July. Coincident with the rise in oestradiol 17β, in the females serum levels of phospho-protein phosphorus and total calcium increased to 400 uβg/ml and 58 mg% respectively just prior to spawning. In the males no significant change in either of these values was observed throughout the cycle. These results strongly support the hypothesis that photoperiod is the major factor in the environmental control of reproductive activity in the rainbow trout.     

孕马血清促性腺激素和氯地酚对猕猴超数排卵效果的观察

用孕马血清促性腺激素,总剂量为1550—2000单位,分4—7天处理猕猴,可促使其每侧卵巢出现滤泡超数发育,随后静脉注射入绒毛膜促性腺激素2500单位,在24小时内,猕猴即可出现超数排卵。     

Radioimmunoassay for reserpine

Antisera against reserpine have been developed in rabbits immunized with reserpine conjugated to bovine serum albumin. These antisera were used in a radioimmunoassay procedure for reserpine. No appreciable cross-reactivity was observed either with reserpine metabolites or with other drugs commonly used in conjunction with reserpine for the treatment of hypertension. The assay was able to detect as little as 150 pg of reserpine in serum (15 ng/ml), without the need for an extraction procedure. Serum concentrations were measured in rats following the oral and intravenous administration of 1 mg/kg of reserpine.     

Plasma somatostatin in normal subjects and in various diseases: increased levels in somatostatin-producing tumors

The plasma levels of somatostatin (SRIF) were studied in normal subjects and patients with various disorders by a sensitive and specific radioimmunoassay. In 45 normal subjects, the fasting plasma SRIF concentrations were 13.3 +/- 5.3 pg/ml (mean +/- SD). Very high concentrations of plasma SRIF, ranging from 125.0 pg/ml to 400.0 pg/ml, were found in all four patients with medullary carcinoma of the thyroid examined and the SRIF levels were changed in parallel with their clinical course after resection of the tumor. A case of pheochromocytoma also showed a relatively high SRIF concentration in plasma (47.0 pg/ml), but the plasma SRIF level decreased to 8.7 pg/ml after removal of the tumor. In normal subjects, plasma SRIF levels did not fluctuate during 2 hr-observation period in basal state. Glucagon (1 mg, iv) and secretin (3 CHRU/kg B.W., iv infusion over 30 min) had no effect on the SRIF levels in the peripheral blood plasma of normal subjects. On intravenous infusion of arginine (0.5 g/kg B.W.) over 30 min, all 6 normal subjects showed a significant increase in plasma SRIF 30-45 min after the start of the infusion (basal value, 11.6 +/- 1.5 pg/ml; peak value, 27.2 +/- 3.0 pg/ml; p less than 0.005). Two cases of medullary thyroid carcinoma showed exaggerated responses after the arginine administration (increases of 103 pg/ml and 157 pg/ml, respectively), suggesting that SRIF was released from the tumor. The findings indicate that plasma SRIF determination in the basal state and after arginine administration is useful for detecting and following up SRIF-producing tumors.     

Isolation,identification and quantitation of serum 5α-pregnane-3,20-dione and its relationship to progesterone in the pregnant mare

5α-pregnane-3,20-dione was isolated from pooled pregnant mare serum using Sephadex LH-20 column chromatography and identified by the use of radioimmunoassay, gas-liquid chromatography and gas-liquid chromatography-mass spectrometry analyses. 5β-pregnane-3,20-dione was not cross-reactive with the radioimmunoassay system and was not detected by gas-liquid chromatography. Peripheral blood levels of progesterone and 5α-pregnane-3,20-dione were determined by radioimmunoassay in four Quarter Horse mares for the first 150 days of gestation. Progesterone and 5α-pregnane-3,20-dione declined from a range of 6 to 15 ng/ml at day 10 to a range of 2 to 8 ng/ml at day 40. After day 40 there was an increase in progesterone and 5α-pregnane-3,20-dione concentration. Toward the end of 150 days of gestation progesterone tended to decline whereas, 5α-pregnane-3,20-dione levels were maintained or increased to levels as high as 35 ng/ml. Neither source nor function of 5α-pregnane-3,20-dione is known.