Search Results
You are looking at 1 - 10 of 43 items for
- Author: F H de Jong x
- Refine by access: All content x
Search for other papers by F. H. DE JONG in
Google Scholar
PubMed
Search for other papers by R. M. SHARPE in
Google Scholar
PubMed
The concentrations of LH and FSH in the plasma and pituitary gland, and testosterone in the plasma and testes were measured in individual rats between 21 and 180 days of age. Spermatogenesis was quantitated in the same animals and correlations between the various parameters were calculated.
The numbers of Sertoli and spermatogenic cells up to pachytene spermatocytes increased in parallel with the peripheral levels of FSH up to days 33 or 35. The concentration of FSH in the plasma started to decrease after day 55, but this decrease could not be correlated with the appearance of any cell type in the testes of the same animals; it was probably due to the high levels of peripheral testosterone at this age. Testicular and plasma levels of testosterone were closely correlated in all age groups studied. The first significant increase occurred between days 39 and 41 and coincided with an increased growth rate of the seminal vesicles and ventral prostate gland. The increase in the concentration of testosterone occurred 10 days after the concentration of LH in the plasma rose to a measurable level. Spermatogenesis had proceeded up to step 16 spermatids at this age.
Search for other papers by F. H. DE JONG in
Google Scholar
PubMed
Search for other papers by R. M. SHARPE in
Google Scholar
PubMed
Peripheral concentrations of FSH in the male rat seem to be regulated in part by a protein hormone, inhibin, which originates from the testes. In an attempt to ascertain which type of testicular cell secretes inhibin, groups of male rats were irradiated prenatally or on days 4, 6 or 8 of postnatal life, and killed at 21, 51 or 81 days of age together with castrated and intact controls. The concentrations of FSH and LH in the pituitary gland, and FSH, LH and testosterone in the plasma were estimated for each animal, and the numbers of each class of intratubular cell in the testes were calculated.
Rats irradiated neonatally had fewer Sertoli cells than controls at all ages studied, while the numbers of Sertoli cells in rats irradiated prenatally were higher than those in controls on day 21. The number of spermatogenic cells was usually decreased in rats irradiated postnatally. In the rats irradiated prenatally normal numbers of spermatogenic cells were found at day 51. Numbers of spermatogenic cells were significantly correlated with the number of Sertoli cells at the ages of 51 and 81 days.
The concentration of FSH in the plasma usually increased in the postnatally irradiated animals on days 21 and 51, but not on day 81; prenatal irradiation did not result in altered levels of FSH at any age. Peripheral levels of LH and testosterone were not affected by irradiation.
The concentration of FSH in the plasma was negatively correlated with the number of Sertoli cells in all age groups, whereas significant correlations between the level of FSH and the number of spermatogenic cells were only found at days 51 and 81. It is concluded from these data that the Sertoli cell is the most likely source of inhibin.
Search for other papers by F. H. de JONG in
Google Scholar
PubMed
Search for other papers by H. J. van der MOLEN in
Google Scholar
PubMed
SUMMARY
A method for the measurement of dehydroepiandrosterone (DHA) and of its sulphate (DHAS) in human peripheral plasma is described and evaluated. After isolation of DHA from the sample the steroid is oxidized to 4-androstene-3,6,17-trione, which is measured with an electron capture detector after gas—liquid chromatography. It is possible to detect 100 pg 4-androstene-3,6,17-trione. The smallest amount of DHA per sample that can be distinguished from zero is approximately 4 ng, when recovery (27·9 ± 8·8%) and method blank (0·23 ± 0·38 ng) are taken into account. The oxidation to 4-ene-3,6-diones is specific for steroidal 5-en-3-ols. Specificity for DHA is ensured by several chromatographic steps. Repeated estimation of 10 ng DHA gave a mean value of 9·6 ± 1·45 (s.d.) ng (n = 35). Mean concentrations and their standard deviations for DHA and DHAS in peripheral plasma from 18 individuals were 0·50 ± 0·25 and 78 ± 40 μg/100 ml, respectively, at 08.30 h and 0·32 ± 0·17 and 84 ± 34 μg/100 ml, respectively, at 17.00 h of the same day. Levels of plasma cortisol in the same plasma samples estimated with a competitive protein-binding method were 16·7 ± 1·8 and 11·9 ± 3·8 μg/100 ml, respectively. No significant differences between the sexes were observed by any of the three assays. The mean values of the plasma concentrations of cortisol and DHA in the morning were significantly higher than those in the evening (P < 0·001 and P < 0·005, respectively). In contrast, the mean value of the plasma levels of DHAS in the morning was significantly lower than that in the evening (P < 0·025).
Search for other papers by A. Perheentupa in
Google Scholar
PubMed
Search for other papers by M. Bergendahl in
Google Scholar
PubMed
Search for other papers by F. H. de Jong in
Google Scholar
PubMed
Search for other papers by I. Huhtaniemi in
Google Scholar
PubMed
ABSTRACT
Direct effects of testosterone on gonadotrophins at the pituitary level were studied in intact and castrated immature (age 10 days) and mature (70 days) male rats. Gonadotrophin-releasing hormone action was blocked by treatment with a potent GnRH antagonist, Ac-d-pClPhe-d-pClPhe-d-Trp-Ser-Tyr-d-Arg-Leu-Arg-Pro-d-Ala-NH2CH3COOH (Ant; Organon 30276; 1·0 mg/kg body weight per day) injected subcutaneously. Silicone elastomer capsules were used for the testosterone treatment. Both treatments commenced on the day of orchiectomy and lasted for 7 days. In adult male rats Ant treatment suppressed serum testosterone from 9·5 ± 2·5 (s.e.m.) nmol/l to below the limit of detection (< 0·10 nmol/l; P < 0·01), and the testosterone implants reversed the decrease. Treatment with Ant decreased the pituitary content of FSH-β subunit mRNA in intact and orchiectomized rats to 14% of their respective controls (P < 0·01). These levels were increased to 80–81% of controls (not significant) in both groups by combined treatment with testosterone and Ant. Orchiectomy alone increased FSH-β subunit mRNA by 202% (P < 0·01). In intact immature rats Ant treatment decreased the level of pituitary FSH-β subunit mRNA to 21% (P<0·01), and a partial recovery (P < 0·01) to 42% of controls was observed with combined Ant + testosterone treatment. In contrast, in orchiectomized immature rats, where ANT decreased FSH-β subunit levels to 48% of controls (P < 0·01), testosterone was able to reverse these mRNA levels completely (114% of controls). No evidence for the direct pituitary effects of testosterone were found in the mRNA of the common α or LH-β subunits. In adult rats, the testicular inhibin α and βA subunit mRNA levels were increased (P < 0·01) by Ant + testosterone compared with Ant-treated animals, but there were no differences in serum immunoreactive inhibin between any of the uncastrated adult groups. In intact immature rats, Ant + testosterone treatment increased (P < 0·01) inhibin βA subunit mRNA levels compared with controls and Ant-treated animals. Ant decreased the level of peripheral inhibin immunoreactivity from 8·3 ± 2·0 U/ml to 2·1 ± 0·4 U/ml (P < 0·01) and testosterone reversed it to 5·8 ± 0·6 U/ml (not significant).
In conclusion, our observations indicated that testosterone is able to stimulate FSH gene expression and secretion directly in immature and adult rats, but the testosterone response is enhanced at both ages by orchiectomy, even more so in the immature rat. This may be explained by age differences in the contribution of testicular inhibin to the regulation of FSH synthesis and secretion at the pituitary level.
Journal of Endocrinology (1993) 137, 69–79
Search for other papers by A. M. Ultee-van Gessel in
Google Scholar
PubMed
Search for other papers by F. H. de Jong in
Google Scholar
PubMed
ABSTRACT
The influence of age on testicular inhibin in untreated, neonatally hemicastrated and prenatally irradiated rats was studied using in-vivo and in-vitro experiments.
In testicular cytosols prepared from 1-, 7-, 14-, 21-, 42- and 63-day-old rats concentrations of testicular inhibin could be measured with an in-vitro bioassay method using dispersed pituitary cells. Preparations of testicular cytosols caused a dose-dependent suppression of pituitary FSH secretion, whereas no effects were found on LH secretion. Testicular content of inhibin increased gradually with age, while after 14 days of age a relatively large increase of peripheral FSH concentrations occurred in all experimental groups. Neonatal hemicastration or prenatal irradiation resulted in decreased inhibin content of the testis and increased plasma FSH levels.
The production of inhibin activity by Sertoli cells obtained from 7-, 14-, 21-, 42- and 63-day-old normal rats was measured during a 24-h incubation period on the third day of culture. The inhibin production per 106 plated Sertoli cells decreased rapidly after 14 days of age and the lowest production of inhibin was found in Sertoli cells from rats of 63 days of age. After preincubation with ovine FSH significantly larger amounts of inhibin activity were detected in spent media from 21-day-old rat testes. In contrast, suppression of inhibin production was found after preculture in the presence of testosterone at most of the ages studied.
These data from in-vivo and in-vitro experiments indicate that a reciprocal relationship exists between pituitary FSH secretion and inhibin production before the age of 21 days. This relationship supports the concept that inhibin is a physiologically important modulator of FSH secretion before puberty, while the role of the large amount of testicular inhibin present at the older ages remains to be determined.
J. Endocr. (1987) 113, 103–110
Search for other papers by F. H. DE JONG in
Google Scholar
PubMed
Search for other papers by A. H. HEY in
Google Scholar
PubMed
Search for other papers by H. J. van der MOLEN in
Google Scholar
PubMed
SUMMARY
Concentrations of oestradiol-17β and testosterone were estimated in peripheral venous plasma and testicular venous plasma of adult male rats before and after administration of human chorionic gonadotrophin (HCG) or follicle-stimulating hormone (FSH). The concentration of oestradiol-17β in peripheral plasma, as measured with a radioimmunological technique, was 2·0 ± 0·9 (s.d.) pg/ml (n = 12). Peripheral testosterone concentrations were 2·4 ± 1·8 (s.d.) ng/ml (n = 21). Concentrations of oestradiol-17β and testosterone in testicular venous plasma were significantly higher than those in peripheral plasma. After intravenous administration of HCG (100 i.u.), oestradiol-17β and testosterone concentrations in testicular venous plasma increased significantly. After prolonged s.c. administration of HCG (5 days) the concentration of oestradiol-17β in testicular venous plasma did not change significantly, although the concentration of testosterone increased more than ten times. Intravenous administration of HCG after 5 days of pretreatment with HCG caused a significant increase in oestradiol-17β concentrations in testicular venous plasma. The increase in testosterone concentration was not significant under these conditions.
Intravenous administration of FSH did not change oestradiol-17β or testosterone concentrations in testicular venous plasma.
Search for other papers by F. H. de JONG in
Google Scholar
PubMed
Search for other papers by A. H. HEY in
Google Scholar
PubMed
Search for other papers by H. J. van der MOLEN in
Google Scholar
PubMed
SUMMARY
Concentrations of oestradiol-17β and testosterone were estimated in testicular tissue from intact and hypophysectomized rats. Within 30 min after intravenous injection of human chorionic gonadotrophin (HCG) or follicle-stimulating hormone (FSH) to intact animals the tissue concentrations of both steroids were not significantly changed. Prolonged s.c. administration of HCG (5 days) caused an increase in the tissue levels of both steroids, which was further increased when the prolonged treatment was followed by an intravenous injection with this trophic hormone. FSH had no influence on tissue concentrations of oestradiol-17β or testosterone in hypophysectomized rats.
Assay of separated seminiferous tubules and interstitial tissue indicated that oestradiol-17β and testosterone were mainly localized in the interstitial tissue. Incubations of these constituents showed that oestradiol-17β was produced in the seminiferous tubules, while testosterone was produced in the interstitial compartment.
Search for other papers by H. M. A. MEIJS-ROELOFS in
Google Scholar
PubMed
Search for other papers by J. Th. J. UILENBROEK in
Google Scholar
PubMed
Search for other papers by F. H. de JONG in
Google Scholar
PubMed
Search for other papers by R. WELSCHEN in
Google Scholar
PubMed
SUMMARY
Oestradiol-17β (E2) was measured by radioimmunoassay in the plasma of immature female rats. Maximal E2 levels of 55–60 pg/ml were found at 10–15 days of age; from day 25 to day 35 E2 levels were low to undetectable. The E2 measured appeared to be of ovarian origin: ovariectomy performed on day 13 resulted in a decreased E2 level 2 days later (13 pg/ml) as compared with the value from the control litter mates (46 pg/ml); after adrenalectomy the level of circulating E2 remained normal (54 pg/ml). The effects of ovariectomy and adrenalectomy on uterine weights followed a similar pattern: ovariectomy resulted in a decrease and adrenalectomy in no change in uterine weight.
In the strain of rat used, levels of follicle-stimulating hormone (FSH) in the serum (measured by radioimmunoassay) were high from day 10 to day 20 and showed a steep decrease on day 21. After ovariectomy on day 15 this decrease in serum FSH was not observed.
The influence of circulating E2 on serum levels of FSH was studied after ovariectomy followed by treatment with varying doses of oestradiol benzoate. Ovariectomy on day 13 resulted in a significantly increased FSH level 2 days later (1770 ng NIAMD-rat-FSH RP-1/ml) as compared with the value obtained from control animals (1033 ng/ml). This increase was not observed after daily injections of 0·1 μg oestradiol benzoate/100 g body weight.
The results indicate that E2 and FSH concentrations show a similar pattern between 5 and 35 days of age. Furthermore, an inhibitory feedback mechanism between oestrogens and FSH concentrations was found to be operative. The implications of these findings are discussed.
Search for other papers by W. J. de Greef in
Google Scholar
PubMed
Search for other papers by J. Th. J. Uilenbroek in
Google Scholar
PubMed
Search for other papers by F. H. de Jong in
Google Scholar
PubMed
The present study was concerned with a possible involvement of LH in the process of functional luteolysis in the pseudopregnant rat.
Daily injections with 2 μg ovine LH during pseudopregnancy reduced peripheral and ovarian levels of progesterone in intact and hysterectomized rats and in hypophysectomized rats with a pituitary transplant under the kidney capsule. However, a daily dose of 10 μg LH did not alter the levels of progesterone. A short-lasting decrease in plasma progesterone occurred when endogenous levels of LH were temporarily raised in pseudopregnant rats by a single injection of LH releasing hormone (LH-RH). Treatment with LH or LH-RH, however, did not shorten the duration of pseudopregnancy.
Daily treatment of pseudopregnant rats with 5 or 20 ng oestradiol benzoate, but not with 1000 ng, decreased plasma levels of progesterone. On the other hand, daily treatment with oestradiol benzoate did not affect plasma progesterone in pseudopregnant rats which were hypophysectomized and had an ectopic pituitary gland. Plasma levels of LH were not increased in the animals receiving 5 or 20 ng oestradiol benzoate daily, suggesting that the effect of oestradiol benzoate on plasma progesterone is not through an enhanced secretion of LH. Treatment with oestradiol benzoate did not affect the duration of pseudopregnancy.
In conclusion, low doses of LH can reduce peripheral levels of progesterone during pseudopregnancy, but it seems improbable that LH is involved in the process of functional luteolysis. Furthermore, low doses of oestradiol benzoate can also decrease plasma progesterone, but the mechanisms involved are still not understood.
Search for other papers by R. J. M. CROUGHS in
Google Scholar
PubMed
Search for other papers by C. F. TOPS in
Google Scholar
PubMed
Search for other papers by F. H. de JONG in
Google Scholar
PubMed
SUMMARY
The present study describes a radioimmunoassay for plasma adrenocorticotrophin (ACTH) in man with a sensitivity of at least 15 pg/ml. In-vitro studies using various fragments of ACTH showed immunobiological dissociation. However, this phenomenon does not appear to be of major importance in vivo, since stimulation and suppression tests showed overall parallel changes of immunoreactive plasma ACTH and plasma cortisol. The results obtained from patients with various forms of Cushing's syndrome are presented. It is concluded that basal plasma ACTH determinations are useful in the differential diagnosis of Cushing's syndrome and may help in predicting the development of a pituitary tumour after adrenalectomy.
The supranormal plasma cortisol response to i.m. injection of lysinevasopressin in subjects with pituitary-dependent Cushing's syndrome is attributed both to an increased ACTH release by the pituitary and to an excessive response of the hyperplastic adrenal cortex. The i.v. infusion of dexamethasone at a rate of 1 mg/h for 5 h in subjects with pituitarydependent Cushing's syndrome was followed by significant and parallel decreases of both immunoreactive plasma ACTH and plasma cortisol. No rise of plasma ACTH levels was found with insulin-induced hypoglycaemia in subjects with untreated pituitary-dependent Cushing's syndrome.
