Effect of continuous illumination on secretion of pregnane compounds by the rat ovary

Summary Differences in the secretion of pregnance compounds from rats with follicular polycystic ovaries under constant light and with normal preovulatory ovaries under light-dark conditions were compared. The injection of LH greatly increased the secretion of progesterone. 5-pregnane-3,20-dione and 3-hydroxy-5-pregnan-20-one, in both types of ovaries, but the response of the two progesterone metabolites in the polycystic ovaries was low, suggesting low 5-reductase activity.Acknowledgments. The authors thank the Endocrinology Study Section, NIADDK, Bethesda, MD, USA. for their gift of LH. This study was supported by Research Grant No. 466 154 from the Ministry of Education, Science, and Culture, Japan.     

Influences of dehydroepiandrosterone acetate on ovarian oocytes in mature cycling rats

Summary Degeneration of ovarian oocytes occurred to a remarkable extent in rats with polycystic ovaries induced by dehydroepiandrosterone acetate (DHA-Ac) administration. The ratio of degeneration oocytes, compared with the total oocytes examined, finally exceeded 70%.We thank Mrs M. Aikawa and Miss R. Araki for laboratory assistance, and Dr K. Araki and the Institute of Animal Experiments for other help.     

Ovarian stimulation by exogenous gonadotrophins in fetal ethanol-exposed immature rats

Adult pregnant rats were given either an ad libitum liquid diet containing 5% ethanol, a pair fed liquid diet or an ad libitum diet of rat chow and water administered throughout pregnancy and during the nursing period. The female offspring received either pregnant mare's serum gonadotrophin (PMSG) or PMSG followed by human chorionic gonadotrophin (hCG) at 30 days of age. The ovaries of fetal ethanol-exposed animals responded greater to the exogenous gonadotrophins with enhanced ovarian weights, increased numbers of ova shed, greater numbers of corpora lutea and antral follicles, and higher serum progesterone levels than in animals exposed to the control diets during gestation.     

Ovarian stimulation by exogenous gonadotrophins in fetal ethanol-exposed immature rats

Summary Adult pregnant rats were given either an ad libitum liquid diet containing 5% ethanol, a pair fed liquid diet or an ad libitum diet of rat chow and water administered throughout pregnancy and during the nursing period. The female offspring received either pregnant mare's serum gonadotrophin (PMSG) or PMSG followed by human chorionic gonadotrophin (hCG) at 30 days of age. The ovaries of fetal ethanol-exposed animals responded greater to the exogeneous gonadotrophins with enhanced ovarian weights, increased numbers of ova shed, greater numbers of corpora lutea and antral follicles, and higher serum progesterone levels than in animals exposed to the control diets during gestation.     

Gonadostatin and gonadocrinin, polypeptides of ovarian origin with hypophysiotropic activity]

Crude acetic acid extract of Rat ovaries pretreated with pregnant mare serum (PMSG) contains native peptides with two types of separable biological activities: one, molecular weight greater than 10,000 dalton inhibits the secretion of both LH and FSH as stimulated by luteinizing hormone releasing factor (LRF) in a pituitary monolayer culture system and is referred to as gonadostatin; the other, less than 3,500 dalton, stimulates the secretion of gonadotropins and is designated as gonadocrinin. The biological activities of ovarian gonadocrinin can be competitively inhibited by an LRF-analog-antagonist, D-Phe2, D-Trp6-LRF. These ovarian peptides may participate in physiological control of pituitary LH/FSH secretion.     

Apoptosis occurs in granulosa cells but not cumulus cells in the atretic antral follicles in pig ovaries

The porcine antral follicles, 3–6 mm in diameter, were dissected from the ovaries of mature pigs, and then granulosa and cumulus cells were isolated from each follicle. In atretic follicles, high activity of neutral Ca²⁺/Mg²⁺-dependent endonuclease and DNA ladder formation, estimated by electrophoresis, were noted in granulosa cells but not in cumulus cells. Extremely low activity of the endonuclease and no DNA ladder formation were observed in both types of cells obtained from healthy follicles. Moreover, apoptotic cells were observed histochemically among granulosa cells only. A good correlation (r=0.987) between the endonuclease activity of granulosa cells and the progesterone/estradiol ratio of follicular fluid in each follicle was found. These results suggest that apoptosis occurs in granulosa cells but not cumulus cells in the atretic antral follicles in pigs.     

Purification of porcine granulosa cells by continuous Percoll gradient

Granulosa cells purified on a continuous Percoll gradient have considerably increased responsiveness to FSH in formation of cAMP, secretion of progesterone, and 125I[hCG] binding to cells incubated for 4 days in culture.     

CFTR pharmacology

CFTR protein is an ion channel regulated by cAMP-dependent phosphorylation and expressed in many types of epithelial cells. CFTR-mediated chloride and bicarbonate secretion play an important role in the respiratory and gastrointestinal systems. Pharmacological modulators of CFTR represent promising drugs for a variety of diseases. In particular, correctors and potentiators may restore the activity of CFTR in cystic fibrosis patients. Potentiators are also potentially useful to improve mucociliary clearance in patients with chronic obstructive pulmonary disease. On the other hand, CFTR inhibitors may be useful to block fluid and electrolyte loss in secretory diarrhea and slow down the progression of polycystic kidney disease.     

Increased responsiveness of the hypothalamic-pituitary axis to steroid feedback effects in ovariectomized rats treated neonatally with monosodium L-glutamate

Summary Chronic ovariectomized rats treated neonatally with MSG showed reduced circulating concentrations of LH coupled with elevated hypothalamic LHRH stores. Despite the apparent loss of LHRH secretion, the small pituitary glands showed an increased density of LHRH receptors and normal responsiveness to the releasing hormone. The positive feedback effects of progesterone on LH release in oestrogen-primed animals was greatly exaggerated reflecting the build-up of hypothalamic LHRH stores without loss of pituitary responsiveness to LHRH.     

Increased responsiveness of the hypothalamic-pituitary axis to steroid feedback effects in ovariectomized rats treated neonatally with monosodium L-glutamate

Chronic ovariectomized rats treated neonatally with MSG showed reduced circulating concentrations of LH coupled with elevated hypothalamic LHRH stores. Despite the apparent loss of LHRH secretion, the small pituitary glands showed an increased density of LHRH receptors and normal responsiveness to the releasing hormone. The positive feedback effects of progesterone on LH release in oestrogen-primed animals was greatly exaggerated reflecting the build-up of hypothalamic LHRH stores without loss of pituitary responsiveness to LHRH.     

Stimulation of human chorionic gonadotropin and progesterone secretion by tumor promoters,phorbol ester and teleocidin B,in cultured choriocarcinoma cells

Summary Both 12-O-tetradecanoyl-phorbol-1-acetate and teleocidin B stimulated the secretion of human chorionic gonadotropin by cultured choriocarcinoma cells. These tumor promoters also stimulated production of progesterone in the cells. However, the 2 tumor promoters did not exert a marked effect on the cellular binding of epidermal growth factor that also had a stimulatory effect on production of these hormones.     

Comparative study of the 3 beta-hydroxy-delta 5-steroid dehydrogenase activity of the mitochondrial and microsomal fractions of human and cat placentas

Delta 5, 3 beta hydroxysteroid dehydrogenase activity was studied on mitochondrial and microsomal fractions of human and cat placentas. This activity was assessed by measuring the rate of [3H] progesterone formation from [3H] pregnenolone and of [3H] delta 4-androstenedione from [3H] dehydroepiandrosterone (DHA), by a double isotope dilution method. Specific activities measured under initial velocity conditions were similar in both human and cat placentas. However, the kinetics of the reaction with DHA as substrate exhibit a zoological specificity.     

Synthesis and metabolism of vertebrate-type steroids by tissues of insects: a critical evaluation

This review covers the synthesis and the metabolism of vertebrate-type steroids (progesterone, testosterone, estradiol, corticosteroids) by insect tissues and discusses the significance of the reactions for insect physiology. Biosynthesis of vertebrate-type steroids from cholesterol hitherto has been demonstrated in only two insect species, i.e. the water beetle Acilius sulcatus (Coleoptera) and the tobacco hornworm Manduca sexta (Lepidoptera). In Acilius, steroid synthesis is associated with exosecretion (chemical defense). Nothing, however, is known about a physiological role of the C21 steroid conjugate present in ovaries and eggs of Manduca. No synthesis of vertebrate-type steroids was observed in any other insect investigated to date. Most metabolic conversions of steroids by insects concerned oxidoreduction of oxygen groups (hydroxysteroid dehydrogenase activity) and (polar and apolar) conjugate formation. All important enzymatic steps involved in synthesis and catabolism, as known from studies with tissues of vertebrates, were not, or hardly observed. The conclusion is drawn that typical vertebrate-type (C21, C19 and C18) steroids probably do not act as physiologically active substances in insects.     

Reversal of net secretion to net absorption of potassium in rat large intestine by dietary potassium depletion

Feeding rats a diet low in potassium and high in sodium for 2 weeks led to a reversal of net potassium secretion to net potassium absorption in ligated segments of distal large intestine (colon descendens and rectum) under in-vivo conditions. This change in the direction of net potassium transport is probably important for the maintenance of potassium homeostasis.     

Effects of ovarian steroids on superoxide dismutase activity in the rat brain

The levels of manganese superoxide dismutase (MnSOD) and copper-zinc superoxide dismutase (CuZnSOD) were determined in appropriate subcellular fractions prepared from whole brain homogenates of cycling and long-term (3 week) ovariectomized (OVX) Wistar rats, and were compared to the levels found in corresponding samples prepared from OVX rats treated with progesterone (P) or estradiol 17B-benzoate (EB). The activity of both SODs was steady during the estrous cycle, except at proestrus, when MnSOD activity was elevated significantly. Bilateral ovariectomy resulted three weeks later in an increase of the MnSOD activity even higher than that recorded at proestrus. High post-castration MnSOD activity was lowered profoundly by exogenous P (2 mg) or EB (0.5 g), given s.c. to OVX animals 2 h or 24 h before sacrifice. Neither removal of the ovaries nor the hormone treatments affected the activity of CuZnSOD. These results suggest suppressive effects of ovarian steroids on MnSOD activity in the rat brain.     

Specific binding of 3H-progesterone to a plasma protein in the guinea pig fetus]

The presence of a protein that binds specifically and with high affinity to progesterone is found in the plasma of fetal guinea Pig. Progesterone and 5 alpha-dihydroxyprogesterone strongly compete for the 3H-progesterone-protein complex. 5 beta-dihydroxy progesterone, 20 beta-dihydroxyprogesterone, testosterone and synthetic progestagen, R-5020 (17,21-dimethyl-19-norpregna-4, 9-diene-3,20 dione), also compete but less intensely. 17-hydroxyprogesterone, aldosterone, cortisol, oestradiol and oestrone have no effect. The 3H-progesterone-protein, complex has an affinity of Kd = 8.8 +/- 3.5 x 10(-10) M and in sucrose density gradient the sedimentation coefficient is 4.6 S.     

Reversal of net secretion to net absorption of potassium in rat large intestine by dietary potassium depletion

Summary Feeding rats a diet low in potassium and high in sodium for 2 weeks led to a reversal of net potassium secretion to net potassium absorption in ligated segments of distal large intestine (colon descendens and rectum) under in-vivo conditions. This change in the direction of net potassium transport is probably important for the maintenance of potassium homeostasis.The technical assistance of Mrs U. Seeliger is gratefully acknowledged.     

Action of various progestational hormones on the electric activity of the rat myometrium in pregnancy after biovariectomy

8-day-pregnant rats were ovariectomized, then injected im with progestagens and estrogens while their uterine motility and electrical activity were being recorded simultaneously with a strain gauge and 2 bipolar electrodes. The injections, known to maintain pregnancy after ovariectomy, were progesterone 50 mg/kg, progesterone with estradiol 5 mcg/kg, or medroxyprogesterone acetate 25 mg/kg. Base line recordings for 20 minutes showed the normal pregnant state of brief periods of synchromous electrical and mechanical activity. After ovariectomy, untreated controls exhibited increased duration of synchronized mechanical and electrical activity and height of contractions. When any of the 3 progestagen treatments coincided with ovariectomy, synchrony was decreased and the intervening interval lasted longer. These procedures demonstrated how quickly the hormonal deficit due to ovariectomy is compensated for when ablation is performed before placental progesterone synthesis has begun.     

Testosterone secretion by Mongolian gerbil interstitial cells during short-term incubation depends on androgen precursors and serum proteins but not on gonadotrophins

Interstitial cells from the testes of the Mongolian gerbil have been used to investigate the effects of serum proteins on testosterone production stimulated by hCG and steroidal precursors. Short-term incubation of interstitial cells with progesterone or DHEA resulted in a rapid increase of testosterone secretion; this effect was even more pronounced in the presence of calf serum. On the other hand, addition of hCG (10 mIU) had no significant effect on testosterone release during the 30-min incubation. These results demonstrate that the magnitude of the steroidogenic response of short-term incubated interstitial cells is a complex function, mainly of precursor concentrations and binding capacities of serum proteins but not of gonadotrophins.     

Testosterone secretion by Mongolian gerbil interstitial cells during short-term incubation depends on androgen precursors and serum proteins but not on gonadotrophins

Summary Interstitial cells from the testes of the Mongolian gerbil have been used to investigate the effects of serum proteins on testosterone production stimulated by hCG and steroidal precursors. Short-term incubation of interstitial cells with progesterone or DHEA resulted in a rapid increase of testosterone secretion; this effect was even more pronounced in the presence of calf serum. On the other hand, addition of hCG (10 mIU) had no significant effect on testosterone release during the 30-min incubation. These results demonstrate that the magnitude of the steroidogenic response of short-term incubated interstitial cells is a complex function, mainly of precursor concentrations and binding capacities of serum proteins but not of gonadotrophins.8 October 1986