摘要:

Stored rat pituitary growth hormone (GH) is functionally divided into immediately releasable and more stable compartments. These observations are consistent with either intracellular hormone compartmentalization within cells of a functionally homogeneous somatotroph population or summed responses from a heterogeneous population of functionally specialized cell subgroups. We investigated the pituitary's ability to recruit stored rGH to replenish depleted immediate release pools. We used perifused pituitary fragments whose stored rGH was labeled during pre-incubation in the presence of [3H] leucine. Initial immediate release pool depletion was accomplished by continuous exposure to combined 21 mM potassium ion (K+) and 1 mM dibutyryl cyclic AMP (dbcAMP). During a subsequent perifusion period in the presence of either no secretagogue, continuing 21 mM K+, or continuing 1 mM dbcAMP, we examined release of stored [3H]rGH in response to repetitive 15 min pulses of 21 mM K+or 1 mM dbcAMP. Analysis was by specific immunoprecipitation. We had demonstrated that K+and dbcAMP pulses can stimulate repetitive, albeit diminishing, stored [3H]rGH release responses. However, following pre-treatment with combined 21 mM K+and 1 mM dbcAMP: (i) pulses of dbcAMP stimulated almost no stored [3H]rGH release in the presence of 21 mM K+or in the absence of a background secretagogue; and (ii) stored [3H]rGH release in response to pulses of K+was attenuated in the absence of background secretagogue but fully restored in the presence of dbcAMP. Conclusions: (i) at least some individual somatotrophs can compartmentalize stored hormone; and (ii) an active transport system facilitates restoration of somatotroph immediate release pools using stored rGH.

ISSN:0743-5800    

DOI:10.1080/07435809009035917

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

The neurohypophysial hormone oxytocin has previously been found in the ovaries of several animal species. In ruminants ovarian oxytocin is postulated to have a luteolytic function, because of its high concentrations in the corpus luteum. In primates the role of ovarian oxytocin is not known. In the present study we measured the immunoreactive oxytocin and oxytocin-neurophysin content in paired ovaries removed from cynomolgus monkeys (Macaca fascicularis) during the late luteal phase of the cycle (Days 12-14 heluteal phase or Days 26-28 of a menstrual cycle). Each animal was pulsed with synthetic gonadotropin-releasing hormone to maintain normal menstrual cyclicity. The concentration of oxytocin and its neurophysin during the late luteal phase was greater in the non-corpus luteum than corpus luteum-bearing ovary. By high pressure liquid chromatography and bioassay the oxytocin in both the corpus luteal and non-corpus luted ovaries was similar to synthetic and posterior pituitary oxytocin. The finding of high concentrations of immunoreactive oxytocin in the non-corpus luteum-bearing ovary suggests that the function of ovarian oxytocin in primates may not be confined specifically to the corpus luteum.

ISSN:0743-5800    

DOI:10.1080/07435809009035918

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

The present study compared the action of angiotensin II (A-II) in bovine adrenal fasciculata cells (BA) and Y–1 adrenal tumor cells which are sensitive and resistant respectively to its steroidogenic effect. In both models, A-II induced a time and dosedependent inositol phosphate (Ins-Ps) accumulation and calcium influx. However, in Y–1 cells the Ins-Ps production was low and only Ins-P1and Ins-P2were accumulated. The calcium influx in BA cells was observed after 15 seconds and remained linear as long as the hormone was present, whereas in Y–1 cells calcium influx started prior the 15 seconds and reverted to basal values after 45 seconds. The effects of A-II antagonists. Taken together these results demonstrate the presence of functional A-II receptors in both cell types which are coupled to the two main intracellular messenger systems. Thus, the A-II steroidogenic refractoriness of Y–1 cells is probably related to some alteration(s) located beyond the calcium and/or protein kinase C A-II-messenger system.

ISSN:0743-5800    

DOI:10.1080/07435809009035919

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

This study examines the effect of placenta on the evolution of lactogen receptor in virgin pseudopregnant rabbit ovary, adrenal gland and mammary gland. Pseudopregnancy was induced with human chorionic gonadotropin. Does were injected with vehicle or placenta daily beginning on day six of the pseudopregnancy. Vehicle-treated rabbits during pseudopregnancy demonstrated a peak of ovarian lactogen receptor on day eight of pseudopregnancy. After treatment with placental homogenate a shift of this peak to twenty days of pseudopregnancy occurred. Lactogen receptor in adrenal and mammary gland membranes had peak receptor concentrations on day 14 of pseudopregnancy. Injection of placenta induced a shift to day 17 and days 17–20 in mammary and adrenal membranes, respectively. Serum concentrations of progesterone, estradiol, 20αdihydroprogesterone and prolactin in placenta-treated groups were not significantly different from those of vehicle-treated groups. Treatment of pseudopregnant does with a composite of hormones at the concentrations found in placental homogenate produced no modulation of tissue lactogen receptor. Fractionation of 20-day pregnant rabbit placenta revealed that 80% of this activity could be found in the acetone extract while 20% was in the bicarbonate extract. These observations suggest that increases of lactogen receptor in ovary, adrenal and mammary glands occur during pseudopregnancy in rabbits and it is further concluded that placenta can alter these receptor induction patterns to ones similar to those seen in these tissues during pregnancy.

ISSN:0743-5800    

DOI:10.1080/07435809009035920

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

Inhibitors of aromatase are useful for treatment of estrogen-dependent breast cancer and as probes for study of normal physiology. Inhibitors of this enzyme with more favorable properties are necessary since the most extensively utilized inhibitor, aminoglutethimide, lacks specificity and causes frequent side effects. The present study compared the potency and specificity of a new aromatase inhibitor, CGS-16949A, with that of aminoglutethimide in a variety ofinvitroenzyme preparations. CGS-16949A blocked aromatase by 50% in human breast cancer homogenates, live breast cancer cells, human placental microsomes and porcine ovarian microsomes at concentrations of 0.008 to 0.02μM. In contrast, concentrations of 10–25μM of aminoglutethimide were required to inhibit aromatase similarly in these tissues. For human placental microsomes, the Kifor CGS 16949A was 0.17 nM and for aminoglutethimide, 0.54μM. Preincubation studies indicated that CGS-16949A acts by a competitive inhibitory mechanism and not by“suicide inhibitory”properties. With respect to specificity, CGS-16949A had no effect on cholesterol side-chain cleavage activity in rat testicular mitochondria. A 54% reduction in enzyme activity was observed in adrenal mitochondria but only at concentrations five orders of magnitude higher (i.e. 100μM) than required to inhibit aromatase. In contrast, 10μM concentrations of aminoglutethimide blocked cholesterol side-chain cleavage activity in rat testicular and adrenal mitochondria by 67 and 91%, respectively. These data suggest that CGS-16949A has favorable properties as a specific and potent aromatase inhibitor.

ISSN:0743-5800    

DOI:10.1080/07435809009035921

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

Changes in the structure and function of rabbit adrenocortical cells were studied eight weeks after cessation of a cholesterol-enriched diet. The plasma cholesterol level of the treated animals was still modestly elevated. All three zones of the adrenal cortex contained a slightly increased number of intracellular lipid droplets, and greater number of lipid-laden macrophages were located in the inner layers, as revealed by light and electron microscopy. The basal and ACTH-stimulated hormone production by the isolated adrenocortical cells were significantly inhibited compared with those of the controls. A possible causal relationship between the inhibited adrenocortical hormone production and the increased number of macrophages is discussed.

ISSN:0743-5800    

DOI:10.1080/07435809009035922

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor

摘要:

This work evaluated a perifusion system for studying LH secretion from the anterior pituitary (AP) of female mice. Pituitary fragments were challenged with LHRH, and the effluents assayed for LH. In general, the tissue exhibited augmented release to repeated stimulation. In the doseresponse study, the amount of LHRH required to produce maximum and half maximum responses dropped almost 10 fold by the 3rd stimulus. In response to various pulse frequencies LH release increased with the frequency of the 100 nM LHRH dose, but the tissue became refractive to constant nonpulsatile stimulation. Other preparations, subjected to high-frequency 10 nM LHRH pulses, released LH in two distinct episodes. All but the first hour of the response was blocked by cycloheximide, confirming the role of protein synthesis in the sustained release of LH. By varying both the pulse frequency and amplitude, a LHRH protocol was found that produced a proestrous-like surge. Lastly, rat and mouse tissues responded similarly to pulsatile LHRH,±

ISSN:0743-5800    

DOI:10.1080/07435809009035923

出版商:Taylor&Francis    

年代:1990

数据来源: Taylor