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J W Funder

Publications and source records attributed to J W Funder.

At least 145 records · Page 8Linked to original sources
PubMed1989

Studies of the secretion of corticotropin-releasing factor and arginine vasopressin into the hypophysial-portal circulation of the conscious sheep. I. Effect of an audiovisual stimulus and insulin-induced hypoglycemia.

Studies were undertaken to characterize the secretion of corticotropin-releasing factor (CRF) and arginine vasopressin (AVP) into the hypophysial-portal circulation of the conscious sheep. In addition, we examined the temporal relationship between the secretion of these two hypothalamic peptides and the secretion of three pro-opiomelanocortin peptides--adrenocorticotropic hormone (ACTH), ir-beta-endorphin, and ir-alpha-melanocyte-stimulating hormone--and cortisol and determined the effects of an audiovisual emotional stimulus and insulin-induced hypoglycemia on the entire hypothalamic-pituitary-adrenal axis. In the basal state, the secretion of CRF, AVP, the three pro-opiomelanocortin peptides, and cortisol was pulsatile in nature, and three CRF and AVP pulse patterns were observed: a concordant increase in CRF and AVP, an isolated rise in CRF, and an isolated increase in AVP. In 4 of the 5 animals, a 3-min audiovisual stress (barking dog) rapidly increased the plasma levels of all the measured substances, although the magnitude and duration of the effect differed markedly between the animals. Insulin-induced hypoglycemia markedly increased AVP and, to a lesser extent, CRF concentrations in portal plasma and thereby altered the CRF:AVP molar ratio. Although pituitary-adrenal activation was closely correlated with the increased hypothalamic activity, a strict 1:1 concordance between CRF/AVP secretion and ACTH secretion was not seen. The anesthetic ketamine selectively increased portal AVP concentrations to levels which exceeded those attained during hypoglycemia and rapidly activated the pituitary-adrenal axis. We conclude the following: (1) CRF and AVP are secreted by the hypothalamus in a pulsatile fashion; (2) ACTH secretion can be stimulated by increases in either CRF or AVP; (3) the absence of a strict 1:1 concordance between hypothalamic CRF/AVP release and pituitary ACTH secretion during stress may be partly due to the release of additional hypothalamic ACTH secretagogues; (4) the ability of both audiovisual stimuli and insulin-induced hypoglycemia to augment CRF and AVP secretion indicates that the paraventricular hypothalamus may be activated by a variety of neural inputs, and (5) the marked alteration of the CRF:AVP molar ratio during stress suggests that AVP may be an important ACTH secretagogue in vivo in the sheep.

Adrenocorticotropic Hormone↗
PubMed1989

Dopaminergic agents differentially regulate both processing and content of alpha-N-acetylated endorphin and alpha-MSH in the ovine pituitary intermediate lobe.

Hypothalamo-pituitary disconnection (HPD) in the sheep results in a two-fold increase in pituitary intermediate lobe (IL) immunoreactive (ir)-alpha-N-acetylated endorphin (NacEP) and ir-alpha-melanocyte-stimulating hormone (alpha MSH) content. The rise in IL NacEP content is accompanied by a markedly altered pattern of processing, in that NacEP1-27 becomes the dominant molecular species with a complementary fall in Nac alpha-EP and Nac gamma-EP. To determine if these effects reflect the loss of descending dopaminergic neuronal input to the IL, we have chronically treated two groups (n = 4 per group) of normal sheep with the dopamine antagonist haloperidol or the dopamine agonist bromocriptine; a group of HPD sheep were also treated with bromocriptine. Acid extracts of IL were diluted and ir-alpha-MSH and ir-NacEP content determined by radioimmunoassay; aliquots were submitted to reversed-phase HPLC and collected fractions similarly assayed. Bromocriptine lowered ir-NacEP and ir-alpha-MSH by about 30%; on HPLC the ir-NacEP profiles, and perhaps to a lesser extent those for ir-alpha-MSH were qualitatively similar to untreated controls. In contrast, haloperidol increased by about 45% both ir-NacEP and ir-alpha-MSH levels and produced a marked change in the ir-NacEP molecular profile, with NacEP1-27 becoming the predominant molecular form and other species representing only minor components in the chromatogram. In the treated HPD group, bromocriptine partially restored the processing profiles previously observed in HPD animals to those found in untreated intact animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Arginine vasopressin is a much more potent stimulus to ACTH release from ovine anterior pituitary cells than ovine corticotropin-releasing factor. 1. In vitro studies.

Cultured rat and ovine anterior pituitary cells were treated with a range of doses (0.01-1,000 nM) of arginine vasopressin (AVP) and ovine corticotropin-releasing factor (CRF), alone or in combination, and medium and cell content of immunoreactive (ir-)ACTH determined. In rat cells, a dose-response curve to CRF was obtained, with a threshold dose of 0.1 nM; AVP was much less effective alone, but augmented CRF responses when administered with CRF. In ovine pituitary cells AVP markedly stimulated ACTH release in a dose-dependent fashion, and with a threshold of 0.1 nM; in contrast, CRF increased ACTH release over basal only at doses greater than 100 nM. In combination, subthreshold doses of AVP potentiated rat pituitary cell responses to CRF; addition of 1 nM of AVP to varying doses of CRF was more effective in terms of ACTH release than addition of 1 nM of CRF to increasing doses of AVP. In contrast, in ovine cells the addition of 1 nM CRF to increasing doses of AVP elicited a larger ACTH response than the addition of 1 nM AVP to increasing doses of CRF. Dexamethasone pretreatment (5 nM) for 48 h significantly decreased CRF potentiation of AVP-stimulated ACTH release in ovine cells. These studies confirm that CRF is a more potent stimulus of ACTH release than AVP in the rat, and establish that in contrast AVP is a much more potent stimulus of ACTH secretion than CRF in isolated ovine pituitary cells.

Adrenocorticotropic Hormone↗
PubMed1989

Glucocorticoid regulation of proopiomelanocortin gene expression in the pituitary gland of hypothalamopituitary intact and hypothalamopituitary disconnected sheep.

Proopiomelanocortin (POMC) gene expression in the anterior pituitary (AP) gland has previously been shown to be positively regulated by CRF and AVP and negatively regulated by glucocorticoids. In the neurointermediate lobe (NIL) of the pituitary, however, POMC gene expression is under tonic inhibitory dopaminergic control. In the present study we have used hypothalamopituitary intact (HPI), ovariectomized (OVX), and OVX/hypothalamopituitary disconnected (OVX/HPD) ewes to examine direct (i.e. nonhypothalamic) effects of glucocorticoids on POMC gene expression in both the AP and the NIL. There was no difference between POMC mRNA levels in intact and OVX sheep. In intact animals treated with dexamethasone, AP POMC mRNA levels were half those of controls. POMC mRNA levels were increased 3-fold in OVX/HPD sheep, compared with OVX, and lowered by dexamethasone to half OVX/HPD levels. In the NIL, hypothalamopituitary disconnection resulted in slightly higher mean POMC mRNA levels than in intact animals but the large intragroup variation did not allow a significant change. Dexamethasone administration had no effect on NIL levels of POMC mRNA in intact or OVX/HPD sheep.

Animals↗
PubMed1989

Regulation of follicle-stimulating hormone beta and common alpha-subunit messenger ribonucleic acid by gonadotropin-releasing hormone and estrogen in the sheep pituitary.

The effect of gonadotropin-releasing hormone (GnRH) and/or estradiol (E2) on pituitary messenger ribonucleic acid (mRNA) levels of luteinizing hormone beta (LH beta), follicle-stimulating hormone beta (FSH beta) and the common alpha-subunit were determined in anterior pituitary glands from ovariectomized (OVX) ewes. Hypothalamo-pituitary disconnected (HPD) ewes receiving appropriate hormonal treatment were used to assess the relative roles of GnRH and E2 in directly regulating FSH beta and alpha-subunit mRNA levels. Levels of LH beta mRNA were increased in OVX animals compared with intact controls, and E2 treatment of OVX animals significantly reduced mRNA levels of LH beta and FSH beta. HPD substantially reduced FSH beta and alpha-subunit mRNA levels. Treatment of OVX/HPD animals with pulses of GnRH (250 ng/2 h) for 1 week restored FSH beta and alpha-subunit mRNA to OVX levels. Combined GnRH and E2 treatment significantly lowered FSH beta mRNA levels, but resulted in a rise in alpha-subunit mRNA levels. Treatment of OVX/HPD ewes with E2 alone had no effect on FSH beta and alpha-subunit mRNA levels. These findings indicate that E2 acts directly on the pituitary to negatively regulate FSH beta mRNA levels, and to positively regulate alpha-subunit mRNA levels in the presence of GnRH.

Animals↗
PubMed1989

Intrapituitary cell-cell communication regulates ACTH secretion.

Exposure of rat anterior pituitary cells in culture to a cytotoxin specific for CRF-target cells is followed by increased basal ACTH secretion from the remaining cells three days after the last exposure to the cytotoxin. When CRF-target-depleted populations are co-cultured with unexposed pituitary cells ACTH secretion is more than double that predicted in the absence of cell-to-cell interaction. These data provide evidence for an intrapituitary cell-to-cell signalling system modulating ACTH secretion.

Adrenocorticotropic Hormone↗
PubMed1989

Immunolocalization of renal mineralocorticoid receptors with an antiserum against a peptide deduced from the complementary deoxyribonucleic acid sequence.

We have synthesized three peptides corresponding to putative antigenic regions in the immunogenic domain, hinge region, and carboxy-terminus of the protein. A rabbit immunized with a peptide derived from the hinge region of the receptor produced an antiserum which showed 50% displacement with 20 pg peptide at a final serum dilution of 1:35,000. When the antiserum was immunopurified and applied to sections of intact rat and human kidney it stained cells lining segments corresponding to distal tubule, connecting piece, and initial cortical collecting duct, consistent with the known sites of mineralocorticoid action. In both human (formaldehyde-fixed) and rat (Bouin's solution) there was ample evidence for both nuclear and cytoplasmic staining. The thymus, in which previously we have found [3H]aldosterone binding to be below detection limits, showed little or no staining. Western blot analyses demonstrated that the polyclonal antibody recognized an epitope of the expected molecular size. The availability of antibodies to the mineralocorticoid receptor should, thus, facilitate investigation of the steroid specificity-conferring mechanism which allows mineralocorticoids, but not glucocorticoids, access to the nonselective receptor in the kidney.

Amino Acid Sequence↗
PubMed1989

Thyroid hormones and the acquisition and retention of behavioural responses.

Naive rats placed in a plexiglass cylinder from a 15 minute test period show progressive immobility, and retain the immobile response when given a 5-minute retest 24 hours later. In the present study we show that hypothyroidism markedly attenuates the acquisition of the immobile response; that this effect on acquisition is reversed 5-10 minutes after the administration of thyroxine; and that hypothyroid rats treated with a single dose of thyroxine up to 2 hours after the initial test show levels of immobility on re-test indistinguishable from intact rats.

Administration, Oral↗
PubMed1989

The intrarenal localization of mineralocorticoid receptors and 11 beta-dehydrogenase: immunocytochemical studies.

The 11 beta-dehydrogenase (11-DH) component of the microsomal enzyme complex, 11 beta-hydroxysteroid dehydrogenase, has been postulated to be the specificity-conferring mechanism for the renal type I receptor. To this end, the distribution of 11-DH and the type I receptor was studied in rat kidney by immunocytochemistry. 11-DH-like immunostaining (LI) was found in Bouin's fixed tissue, in both nuclear and cytoplasmic components of some cells of the juxtamedullary proximal convoluted tubules, and in interstitial cells of the papillary medulla. In addition, weak staining was seen in superficial proximal convoluted tubules in paraformaldehyde-fixed tissue. Type I receptor-LI was found in distal convoluted tubules, connecting pieces, and initial cortical collecting tubules of the superficial cortex. Since colocalization of the enzyme and receptor was not demonstrated, the action of 11-DH on type I receptor specificity would, thus, appear to be paracrine rather than autocrine.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1989

Vascular type I aldosterone binding sites are physiological mineralocorticoid receptors.

In vitro, Type I receptors have high and equivalent affinity for aldosterone, corticosterone and cortisol: in vivo, physiological mineralocorticoid target tissues (kidney, colon, parotid) are highly aldosterone-selective, in contrast with hippocampus and heart. In the present study we show that the mesenteric vascular arcade is similarly highly aldosterone-selective in vivo, and in vitro shows considerable levels of 11 beta OH steroid dehydrogenase activity, previously postulated as the mechanism whereby glucocorticoids are excluded from physiological mineralocorticoid receptors.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1989

Glucocorticoids regulate ovine hypophysial portal levels of corticotropin-releasing factor and arginine vasopressin in a stress-specific manner.

Hypophysial portal circulation levels of immunoreactive (ir) CRF, immunoreactive arginine vasopressin (ir-AVP), and systemic ir-ACTH and cortisol were determined in dexamethasone-infused (20 micrograms/h) ewes, both under basal conditions and in response to audiovisual and hypoglycemic stress. Glucocorticoid infusion lowered mean basal levels of ir-CRF (P less than 0.05), ir-ACTH (P less than 0.05), and cortisol (P less than 0.05), but not of ir-AVP. Audiovisual stress led to coordinate release of ir-AVP and ir-CRF, and although the hypothalamic response to this stress was not altered in dexamethasone (DEX)-infused sheep, the pituitary-adrenal response was blocked, suggesting that glucocorticoids act on the pituitary rather than on higher centers to inhibit this response. In contrast, hypoglycemia led to preferential release of ir-AVP over ir-CRF, and DEX infusion delayed and inhibited both hypothalamic and pituitary responses. Ketamine injection also led to preferential release of ir-AVP, but neither the hypothalamic nor pituitary-adrenal responses were affected by DEX infusion. These results suggest that different stressors evoke different patterns of hypothalamic secretagogue release, and that glucocorticoids act in a site-specific fashion to regulate the hypothalamo-pituitary-adrenal responses to stress.

Animals↗
PubMed1989

Type I and type II corticosteroid receptor gene expression in the rat: effect of adrenalectomy and dexamethasone administration.

We have used 32P-labeled cRNA probes directed against Type I (mineralocorticoid, high affinity glucocorticoid) and Type II (classical glucocorticoid) receptor mRNA to screen various tissues, and have investigated the effect of adrenalectomy (ADX) and dexamethasone (DM) administration on their levels in hippocampus. Both Northern blot and S1 nuclease analysis showed Type I mRNA to be high in hippocampus, colon, and heart; low in liver; and undetectable in thymus. Type II mRNA was high in liver, thymus, and brain; and low in testis and parotid. A transient increase in both hippocampal Type I and Type II mRNA was noted at 1-3 days post ADX. DM similarly elicited a rise in hippocampal Type I mRNA at 2-4 days after ADX, but prevented the ADX-induced increment in Type II mRNA. In contrast to the transient increase in Type I receptor mRNA levels, hippocampal levels of Type I receptors measured by [3H]aldosterone binding were constant 1-16 days post ADX. DM administration caused a doubling in Type I receptor levels over 4 days, with plateau levels at 4-16 days; previously, DM has been shown to lower Type II receptor levels in the hippocampus.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy↗
PubMed1989

Hormonal regulation of gene expression.

In this presentation, three facets of the topic will be addressed: signal specificity, receptor specificity and kinetics. First, both clinical and co-transfection studies show cortisol to be a potent mineralocorticoid agonist when it occupies Type I (mineralocorticoid) receptors. Cytosol Type I receptors from various tissues, and recombinant-derived human renal mineralocorticoid receptors, show equivalent affinity in vitro for aldosterone and for cortisol, which circulates at approximately 100-fold higher levels. In vivo, aldosterone specificity of Type I receptors in physiological mineralocorticoid target tissues reflects local metabolism of cortisol (but not of aldosterone), to receptor-inactive cortisone, by the microsomal enzyme 11 beta OH steroid dehydrogenase. Secondly, alpha-lactalbumin synthesis in the mid-pregnant rat mammary gland explant is stimulated by very low doses of glucocorticoids, but progressively inhibited at higher doses, and is exquisitely sensitive to progestin blockade. To reconcile these data, we have developed a model of transcriptional regulation involving multiple overlapping glucocorticoid and progesterone regulatory elements. Finally, in the Porsolt swimming rat model, the effect of adrenalectomy on a learned response is reversed by glucocorticoid administration up to an hour after the conditioning experiment.

Aldosterone↗
PubMed1988

Androgen dependence of specific kallikrein gene family members expressed in rat prostate.

We have used oligonucleotide probes specific for members of the rat kallikrein/tonin gene family (PS, S1, S2, S3, K1, and P1) to establish which arginyl esteropeptidase (kallikrein-like) genes are expressed in the prostate. We have also compared the expression and androgen dependence of these genes in prostate, submaxillary gland (SMG) and kidney. Only S3 (tonin-like) and P1 (kallikrein-like) are expressed in the prostate, with S3 very much more abundant. Prostatic S3 mRNA disappears after 8 days castration and is restored to intact levels by dihydrotestosterone (DHT) but not estradiol benzoate (EB) for 8 days. Prostate P1 mRNA levels were similarly but not identically affected. All six genes are expressed in the SMG, with PS (true kallikrein) the most abundant. Levels of PS mRNA in SMG are unaffected by castration, DHT, or EB treatment, although mRNA levels of other kallikrein-like (S1, K1, and P1), tonin (S2), and tonin-like (S3) genes fall 40-60% after castration, and are unaffected or partially restored by DHT and/or EB administration. Only PS and K1 are expressed in the kidney, at much lower levels than in the SMG and unaffected by castration or steroids. These studies thus confirm and extend the concept of tissue specificity of arginyl esteropeptidase gene expression, and further demonstrate that the same gene(s) is differentially regulated by androgens in the rat prostate, SMG, and kidney.

Animals↗
PubMed1988

Mineralocorticoid action: target tissue specificity is enzyme, not receptor, mediated.

Mineralocorticoid receptors, both when in tissue extracts and when recombinant-derived, have equal affinity for the physiological mineralocorticoid aldosterone and for the glucocorticoids cortisol and corticosterone, which circulate at much higher concentrations than aldosterone. Such receptors are found in physiological mineralocorticoid target tissues (kidney, parotid, and colon) and in nontarget tissues such as hippocampus and heart. In mineralocorticoid target tissues the receptors are selective for aldosterone in vivo because of the presence of the enzyme 11 beta-hydroxy-steroid dehydrogenase, which converts cortisol and corticosterone, but not aldosterone, to their 11-keto analogs. These analogs cannot bind to mineralocorticoid receptors.

Adrenalectomy↗
PubMed1988

Steroid receptors, and the generation of closely coupled/biphasic dose-response curves.

In most steroid-modulated systems, responses are closely coupled to receptor occupancy, with half-maximal responses at Kd, and near-maximal at greater than or equal to 10 Kd. Though glucocorticoids have been reported to increase, and progesterone to lower, levels of various milk proteins, clear differences in glucocorticoid dose-response profiles have been previously described. In mouse mammary gland explants in vitro, Ono and Oka showed that casein synthesis was stimulated by cortisol to plateau levels with progressively higher doses; in contrast, the dose-response curve for alpha-lactalbumin (alpha-LA) was biphasic, with stimulation at low doses and a return to baseline at higher cortisol levels. Since cortisol is both non-physiologic in the mouse, and has higher affinity for Type I (mineralocorticoid-like) than Type II (glucocorticoid) receptors, this might reflect an induction of alpha-LA synthesis via Type I receptor occupancy, and a suppression via Type II receptor occupancy. To examine this possibility we have used highly selective Type II receptor ligands, and in addition have defined the role of progestins as candidate inhibitors of alpha-LA synthesis. We have thus incubated mid-pregnant rat mammary gland explants in medium including insulin and prolactin, with increasing concentrations of highly specific Type II ligand (RU26988 or RU28362) and/or the selective progestin ORG 2058, and determined tissue and medium content of alpha-LA 48 h later. RU26988/RU28362 increased alpha-LA to a maximum of 3-6-fold basal at approximately 3 nM, well below the Kd (37 degrees C) for Type II receptors (8-28 nM); levels fell progressively with increasing concentration of ligand, returning to baseline by 30-300 nM. ORG 2058 lowered both basal and RU26988-stimulated levels, with the half-maximally effective dose being approximately 10(-10) M, again well below Kd for receptor binding. To accommodate the observed biphasic dose-response curve for highly specific glucocorticoids, and the shift-to-the-left for both classes of effector, we have proposed a model of a single "turn-on" nuclear acceptor site for glucocorticoid receptors (glucocorticoid regulatory element: GRE) and multiple, pre-emptive "turn-off" GREs, occupancy of any one of which will abrogate transcription; for progestins, we propose that all the GRE are alternate "turn-off" sites. Consistent with such a hypothesis, Qasba and Safaya have shown that the alpha-LA genome contains six core consensus sequences (TGT TCCT) which are putative GRE, and von der Ahe et al. that both progesterone receptors and glucocorticoid receptors may bind to GRE sites.

Androstanols↗
PubMed1988

Photoaffinity labelling with [3H]R1881 of androgen receptors from human cultured genital fibroblasts of normal individuals and patients with androgen receptor abnormalities.

Androgen receptors were partially purified by affinity chromatography of cytosols prepared from cultured genital fibroblasts of normal individuals and patients with androgen receptor abnormalities. Partially purified receptors were covalently labelled with [3H]R1881 (triated methyltrienolone) by ultraviolet photoactivation. Gel electrophoresis of cytosols from normal individuals showed a single radioactive peak, Mr approximately 97 K. Cytosols from patients with decreased nuclear transfer showed a similar peak, Mr approximately 97 K; cytosols from patients with partial androgen insensitivity (PAIS) or receptor positive complete androgen insensitivity (CAIS, R+) showed a peak Mr approximately 30 K-43 K.

Affinity Labels↗